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Sample records for molar extinction coefficient

  1. Molar extinction coefficients of some fatty acids

    DEFF Research Database (Denmark)

    Sandhu, G.K.; Singh, K.; Lark, B.S.

    2002-01-01

    ) and stearic acid (C18H36O2), has been measured at the photon energies 81, 356, 511, 662, 1173 and 1332 keV. Experimental values for the molar extinction coefficient, the effective atomic number and the electron density have been derived and compared with theoretical calculations. There is good agreement......The attenuation of gamma rays in some fatty acids, viz. formic acid (CH2O2), acetic acid (C2H4O2), propionic acid (C3H6O2), butyric acid (C4H8O2), n-hexanoic acid (C6H12O2), n-caprylic acid (C8H16O2), lauric acid (C12H24O2), myristic acid (C14H28O2), palmitic acid (C16H32O2), oleic acid (C18H34O2...

  2. Molar extinction coefficients of solutions of some organic compounds

    Indian Academy of Sciences (India)

    efficients of these compounds have been used to calculate effective atomic numbers and electron densities. The additivity ... Molar extinction coefficients; effective atomic numbers; electron density. PACS Nos 29.30. ... the radiation path and is linearly dependent on the concentration of the absorbing species. This is most ...

  3. Molar extinction coefficients of solutions of some organic compounds

    Indian Academy of Sciences (India)

    (C4H8O2), succinimide (C4H5NO2) as estimated from the measured absorbance of. 7 radiations in their ... species in the solution and ε is called the molar absorptivity or extinction coefficient. (l mol-1cm-1 or ... Integration of eq. (4) leads to.

  4. Molar extinction coefficients of some carbohydrates in aqueous ...

    Indian Academy of Sciences (India)

    of plants and animals, both as structural elements and in the maintenance of functional ... In this paper we report the molar extinction coefficient ε, of carbohydrates ... as the area, which has to be hit by the photons in order to cause interaction.

  5. Molar extinction coefficients of some commonly used solvents

    International Nuclear Information System (INIS)

    Kumar, Ashok; Singh, Sukhpal; Singh Mudahar, Gurmel; Singh Thind, Kulwant

    2006-01-01

    Molar extinction coefficients of some commonly used solvents (ethanol (C 2 H 5 OH), methanol (CH 3 OH), propanol (C 3 H 7 OH), butanol (C 4 H 9 OH), water (H 2 O), toluene (C 7 H 8 ), benzene (C 6 H 6 ), carbontetrachloride (CCl 4 ), acetonitrile (C 4 H 3 N), chlorobenzene (C 6 H 5 Cl), diethylether (C 4 H 1 O) and dioxane (C 4 H 8 O 2 )) have been determined by a well-collimated narrow beam transmission geometry at 279, 356, 662, 1173, 1252 and 1332 keV γ rays. The total γ ray interaction cross sections of these solvents have also been determined. A good agreement has been obtained between the experimental results with the theoretical values evaluated through XCOM calculations

  6. Determination of the molar extinction coefficient for the ferric reducing/antioxidant power assay.

    Science.gov (United States)

    Hayes, William A; Mills, Daniel S; Neville, Rachel F; Kiddie, Jenna; Collins, Lisa M

    2011-09-15

    The FRAP reagent contains 2,4,6-tris(2-pyridyl)-s-triazine, which forms a blue-violet complex ion in the presence of ferrous ions. Although the FRAP (ferric reducing/antioxidant power) assay is popular and has been in use for many years, the correct molar extinction coefficient of this complex ion under FRAP assay conditions has never been published, casting doubt on the validity of previous calibrations. A previously reported value of 19,800 is an underestimate. We determined that the molar extinction coefficient was 21,140. The value of the molar extinction coefficient was also shown to depend on the type of assay and was found to be 22,230 under iron assay conditions, in good agreement with published data. Redox titration indicated that the ferrous sulfate heptahydrate calibrator recommended by Benzie and Strain, the FRAP assay inventors, is prone to efflorescence and, therefore, is unreliable. Ferrous ammonium sulfate hexahydrate in dilute sulfuric acid was a more stable alternative. Few authors publish their calibration data, and this makes comparative analyses impossible. A critical examination of the limited number of examples of calibration data in the published literature reveals only that Benzie and Strain obtained a satisfactory calibration using their method. Copyright © 2011 Elsevier Inc. All rights reserved.

  7. A High Molar Extinction Coefficient Mono-Anthracenyl Bipyridyl Heteroleptic Ruthenium(II Complex: Synthesis, Photophysical and Electrochemical Properties

    Directory of Open Access Journals (Sweden)

    Peter A. Ajibade

    2011-06-01

    Full Text Available In our quest to develop good materials as photosensitizers for photovoltaic dye-sensitized solar cells (DSSCs, cis-dithiocyanato-4-(2,3-dimethylacrylic acid-2,2'-bipyridyl-4-(9-anthracenyl-(2,3-dimethylacrylic-2,2'-bipyridyl ruthenium(II complex, a high molar extinction coefficient charge transfer sensitizer, was designed, synthesized and characterized by spectroscopy and electrochemical techniques. Earlier studies on heteroleptic ruthenium(II complex analogues containing functionalized oligo-anthracenyl phenanthroline ligands have been reported and documented. Based on a general linear correlation between increase in the length of π-conjugation bond and the molar extinction coefficients, herein, we report the photophysical and electrochemical properties of a Ru(II bipyridyl complex analogue with a single functionalized anthracenyl unit. Interestingly, the complex shows better broad and intense metal-to ligand charge transfer (MLCT band absorption with higher molar extinction coefficient (λmax = 518 nm, e = 44900 M−1cm−1, and appreciable photoluminescence spanning the visible region than those containing higher anthracenyl units. It was shown that molar absorption coefficient of the complexes may not be solely depended on the extended π-conjugation but are reduced by molecular aggregation in the molecules.

  8. Molar extinction coefficients and other properties of an improved reaction center preparation from Rhodopseudomonas viridis

    Energy Technology Data Exchange (ETDEWEB)

    Clayton, R.K.; Clayton, B.J.

    1978-01-01

    Reaction centers have been purified from chromatophores of Rhodopseudomonas viridis by treatment with lauryl dimethyl amine oxide followed by hydroxyapatite chromatography and precipitation with ammonium sulfate. The absorption spectrum at low temperature shows bands at 531 and 543 nm, assigned to two molecules of bacteriopheophytin b. The 600 nm band of bacteriochlorophyll b is resolved at low temperature into components at 601 and 606.5 nm. At room temperature the light-induced difference spectrum shows a negative band centered at 615 nm, where the absorption spectrum shows only a week shoulder adjacent to the 600 nm band. The fluorescence spectrum shows a band at 1000 nm and no fluorescence corresponding to the 830 nm absorption band. Two molecules of cytochrome 558 and three of cytochrome 552 accompany each reaction center. The differential extinction coefficient (reduced minus oxidized) of cytochrome 558 nm was estimated as 20 +- 2 mM/sup -1/.cm/sup -1/ through a coupled reaction with equine cytochrome c. The extinction coefficient of reaction centers at 960 nm was determined to be 123 +- 25 mM/sup -1/.cm/sup -1/ by measuring the light-induced bleaching of P-960 and the coupled oxidation of cytochrome 558. The corresponding extinction coefficient at 830 nm is 300 +- 65 mM/sup -1/.cm/sup -1/. The absorbance ratio ..cap alpha../sub 280nm/..cap alpha../sub 830nm/ in our preparations was 2.1, and there was 190 kg protein per mol of reaction centers. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed three major components of apparent molecular weights 31,000, 37,000, and 41,000.

  9. A subtle calculation method for nanoparticle’s molar extinction coefficient: The gift from discrete protein-nanoparticle system on agarose gel electrophoresis

    Science.gov (United States)

    Zhong, Ruibo; Yuan, Ming; Gao, Haiyang; Bai, Zhijun; Guo, Jun; Zhao, Xinmin; Zhang, Feng

    2016-03-01

    Discrete biomolecule-nanoparticle (NP) conjugates play paramount roles in nanofabrication, in which the key is to get the precise molar extinction coefficient of NPs. By making best use of the gift from a specific separation phenomenon of agarose gel electrophoresis (GE), amphiphilic polymer coated NP with exact number of bovine serum albumin (BSA) proteins can be extracted and further experimentally employed to precisely calculate the molar extinction coefficient of the NPs. This method could further benefit the evaluation and extraction of any other dual-component NP-containing bio-conjugates.

  10. Calculation extinction cross sections and molar attenuation coefficient of small gold nanoparticles and experimental observation of their UV-vis spectral properties

    Science.gov (United States)

    Tang, Junqi; Gao, Kunpeng; Ou, Quanhong; Fu, Xuewen; Man, Shi-Qing; Guo, Jie; Liu, Yingkai

    2018-02-01

    Gold nanoparticles (AuNPs) have been researched extensively, such as applied in various biosensors, biomedical imaging and diagnosis, catalysis and physico-chemical analysis. These applications usually required to know the nanoparticle size or concentration. Researchers have been studying a simply and quick way to estimate the concentration or size of nanoparticles from their optical spectra and SPR feature for several years. The extinction cross-sections and the molar attenuation coefficient were one of the key parameters. In this study, we calculated the extinction cross-sections and molar attenuation coefficient (decadic molar extinction coefficient) of small gold nanoparticles by dipole approximation method and modified Beer-Lambert law. The theoretical result showed that the surface plasmon resonance peak of small gold nanoparticles was blueshift with an increase size. Moreover, small AuNPs (sub-10 nm) were prepared by using of dextran or trisodium citrate as reducing agent and capping agent. The experimental synthesized AuNPs was also shows a blueshift as increasing particle size in a certain range. And the concentration of AuNPs was calculated based on the obtained molar attenuation coefficient. For small nanoparticles, the size of nanoparticles and surface plasmon resonance property was not showed a positive correlation compared to larger nanoparticles. These results suggested that SPR peak depended not only on the nanoparticle size and shape but also on the nanoparticles environment.

  11. High Molar Extinction Coefficient Ru(II-Mixed Ligand Polypyridyl Complexes for Dye Sensitized Solar Cell Application

    Directory of Open Access Journals (Sweden)

    Malapaka Chandrasekharam

    2011-01-01

    Full Text Available Two new ruthenium(II mixed ligand terpyridine complexes, “Ru(Htcterpy(NCS(L1 (N(C4H94, mLBD1” and Ru(Htcterpy(NCS(L2(N(C4H94, mLBD2 were synthesized and fully characterized by UV-Vis, emission, cyclic voltammogram, and other spectroscopic means, and the structures of the compounds are confirmed by 1H-NMR, ESI-MASS, and FT-IR spectroscopes. The influence of the substitution of L1 and L2 on solar-to-electrical energy conversion efficiency (η of dye-sensitized solar cells (DSSCs was evaluated relative to reference black dye. The dyes showed molar extinction coefficients of 17600 M−1 cm−1 for mLBD1 and 21300 M−1 cm−1 for mLBD2 both at λ maximum of 512 nm, while black dye has shown 8660 M−1 cm−1 at λ maximum of 615 nm. The monochromatic incident photon-to-collected electron conversion efficiencies of 60.71% and 75.89% were obtained for mLBD1 and mLBD2 dyes, respectively. The energy conversion efficiencies of mLBD1 and mLBD2 dyes are 3.15% (SC=11.86 mA/cm2, OC=613 mV, ff=0.4337 and 3.36% (SC=12.71 mA/cm2, OC=655 mV, ff=0.4042, respectively, measured at the AM1.5G conditions, the reference black dye-sensitized solar cell, fabricated and evaluated under identical conditions exhibited η-value of 2.69% (SC=10.95 mA/cm2, OC=655 mV, ff=0.3750.

  12. DFT-INDO/S modeling of new high molar extinction coefficient charge-transfer sensitizers for solar cell applications.

    Science.gov (United States)

    Nazeeruddin, Mohammad K; Wang, Qing; Cevey, Le; Aranyos, Viviane; Liska, Paul; Figgemeier, Egbert; Klein, Cedric; Hirata, Narukuni; Koops, Sara; Haque, Saif A; Durrant, James R; Hagfeldt, Anders; Lever, A B P; Grätzel, Michael

    2006-01-23

    A new ruthenium(II) complex, tetrabutylammonium [ruthenium (4-carboxylic acid-4'-carboxylate-2,2'-bipyridine)(4,4'-di(2-(3,6-dimethoxyphenyl)ethenyl)-2,2'-bipyridine)(NCS)(2)] (N945H), was synthesized and characterized by analytical, spectroscopic, and electrochemical techniques. The absorption spectrum of the N945H sensitizer is dominated by metal-to-ligand charge-transfer (MLCT) transitions in the visible region, with the lowest allowed MLCT bands appearing at 25 380 and 18 180 cm(-1). The molar extinction coefficients of these bands are 34 500 and 18 900 M(-1) cm(-1), respectively, and are significantly higher when compared to than those of the standard sensitizer cis-dithiocyanatobis(4,4'-dicarboxylic acid-2,2'-bipyridine)ruthenium(II). An INDO/S and density functional theory study of the electronic and optical properties of N945H and of N945 adsorbed on TiO(2) was performed. The calculations point out that the top three frontier-filled orbitals have essentially ruthenium 4d (t(2g) in the octahedral group) character with sizable contribution coming from the NCS ligand orbitals. Most critically the calculations reveal that, in the TiO(2)-bound N945 sensitizer, excitation directs charge into the carboxylbipyridine ligand bound to the TiO(2) surface. The photovoltaic data of the N945 sensitizer using an electrolyte containing 0.60 M butylmethylimidazolium iodide, 0.03 M I(2), 0.10 M guanidinium thiocyanate, and 0.50 M tert-butylpyridine in a mixture of acetonitrile and valeronitrile (volume ratio = 85:15) exhibited a short-circuit photocurrent density of 16.50 +/- 0.2 mA cm(-2), an open-circuit voltage of 790 +/- 30 mV, and a fill factor of 0.72 +/- 0.03, corresponding to an overall conversion efficiency of 9.6% under standard AM (air mass) 1.5 sunlight, and demonstrated a stable performance under light and heat soaking at 80 degrees C.

  13. Prediction of Molar Extinction Coefficients of Proteins and Peptides Using UV Absorption of the Constituent Amino Acids at 214 nm To Enable Quantitative Reverse Phase High-Performance Liquid Chromatography-Mass Spectrometry Analysis

    NARCIS (Netherlands)

    Kuipers, B.J.H.; Gruppen, H.

    2007-01-01

    The molar extinction coefficients of 20 amino acids and the peptide bond were measured at 214 nm in the presence of acetonitrile and formic acid to enable quantitative comparison of peptides eluting from reversed-phase high-performance liquid chromatography, once identified with mass spectrometry

  14. Extinction Coefficient of Gold Nanostars

    OpenAIRE

    de Puig, Helena; Tam, Justina O.; Yen, Chun-Wan; Gehrke, Lee; Hamad-Schifferli, Kimberly

    2015-01-01

    Gold nanostars (NStars) are highly attractive for biological applications due to their surface chemistry, facile synthesis and optical properties. Here, we synthesize NStars in HEPES buffer at different HEPES/Au ratios, producing NStars of different sizes and shapes, and therefore varying optical properties. We measure the extinction coefficient of the synthesized NStars at their maximum surface plasmon resonances (SPR), which range from 5.7 × 108 to 26.8 × 108 M−1cm−1. Measured values correl...

  15. Extinction Coefficient of Gold Nanostars.

    Science.gov (United States)

    de Puig, Helena; Tam, Justina O; Yen, Chun-Wan; Gehrke, Lee; Hamad-Schifferli, Kimberly

    2015-07-30

    Gold nanostars (NStars) are highly attractive for biological applications due to their surface chemistry, facile synthesis and optical properties. Here, we synthesize NStars in HEPES buffer at different HEPES/Au ratios, producing NStars of different sizes and shapes, and therefore varying optical properties. We measure the extinction coefficient of the synthesized NStars at their maximum surface plasmon resonances (SPR), which range from 5.7 × 10 8 to 26.8 × 10 8 M -1 cm -1 . Measured values correlate with those obtained from theoretical models of the NStars using the discrete dipole approximation (DDA), which we use to simulate the extinction spectra of the nanostars. Finally, because NStars are typically used in biological applications, we conjugate DNA and antibodies to the NStars and calculate the footprint of the bound biomolecules.

  16. A High Molar Extinction Coefficient Ru(II Complex Functionalized with cis-Dithiocyanato-bis-(9-anthracenyl-10-(2-methyl-2-butenoic acid-1,10-phenanthroline: Potential Sensitizer for Stable Dye-Sensitized Solar Cells

    Directory of Open Access Journals (Sweden)

    Adewale O. Adeloye

    2014-01-01

    Full Text Available New heteroleptic ruthenium(II complex was formulated as [Ru(L12(NCS2], where L1 = 9-anthracenyl-10-(2-methyl-2-butenoic acid-1,10-phenanthroline was synthesized and its photophysical properties were studied and compared to previously reported analogue complex containing no anthracene moiety [Ru(L22(NCS2], L2 = (2-methyl-2-butenoic acid-1,10-phenanthroline. The two complexes though exhibit very strong molar extinction coefficient values; however, [Ru(L12(NCS2] shows better characteristic broad and intense metal-to-ligand charge transfer (MLCT absorption band and higher molar absorptivity coefficient at (λmax=522 nm, ε=6.60×104 M−1 cm−1 than that of [Ru(L22(NCS2] complex, (λmax=446 nm, ε=4.82×104 M−1 cm−1. At room temperature, long wavelength emissions with strong intensity ratio centered at 660 nm were recorded for [Ru(L12(NCS2] complex with a bathochromic shift (λem=700 nm for [Ru(L22(NCS2] complex. It was shown that the luminescence wavelength characteristic of the complexes may be a function relating to the increasing length of π-conjugation and/or molecular weight. A preliminary cyclic voltammetry of [Ru(L12(NCS2] complex also exhibits good electroredox activity with oxidation potential of about 1.04 V, significantly better than other Ru(II polypyridine complexes containing bidentate ligands.

  17. Theoretical investigation of the extinction coefficient of magnetic fluid

    Energy Technology Data Exchange (ETDEWEB)

    Fang Xiaopeng; Xuan Yimin, E-mail: ymxuan@mail.njust.edu.cn; Li Qiang [Nanjing University of Science and Technology, School of Energy and Power Engineering (China)

    2013-05-15

    A new theoretical approach for calculating the extinction coefficient of magnetic fluid is proposed, which is based on molecular dynamics (MD) simulation and T-matrix method. By means of this approach, the influence of particle diameter, particle volume fraction, and external magnetic filed on the extinction coefficient of magnetic fluid is investigated. The results show that the extinction coefficient of the magnetic fluid linearly increases with increase in the particle volume fraction. For a given particle volume fraction, the extinction coefficient increases with increase in the particle diameter which varies from 5 to 20 nm. When a uniform external magnetic filed is applied to the magnetic fluid, the extinction coefficient of the magnetic fluid presents an anisotropic feature. These results agree well with the reported experimental results. The proposed approach is applicable to investigating the optical properties of magnetic fluids.

  18. Simultaneous all-optical determination of molecular concentration and extinction coefficient.

    Science.gov (United States)

    Cho, Byungmoon; Tiwari, Vivek; Jonas, David M

    2013-06-04

    Absolute molecular number concentration and extinction coefficient are simultaneously determined from linear and nonlinear spectroscopic measurements. This method is based on measurements of absolute femtosecond pump-probe signals. Accounting for pulse propagation, we present a closed form expression for molecular number concentration in terms of absorbance, fluorescence, absolute pump-probe signal, and laser pulse parameters (pulse energy, spectrum, and spatial intensity profile); all quantities are measured optically. As in gravimetric and coulometric determinations of concentration, no standard samples are needed for calibration. The extinction coefficient can then be determined from the absorbance spectrum and the concentration. For fluorescein in basic methanol, the optically determined molar concentrations and extinction coefficients match gravimetric determinations to within 10% for concentrations from 0.032 to 0.540 mM, corresponding to absorbance from 0.06 to 1. In principle, this photonumeric method is extensible to transient chemical species for which other methods are not available.

  19. Molecular extinction coefficients of lead sulfide and polymerized diaminobenzidine as final reaction products of histochemical phosphatase reactions

    NARCIS (Netherlands)

    van Noorden, C. J.; Jonges, G. N.

    1992-01-01

    Molar extinction coefficients of precipitated lead sulfide (PbS) and polymerized diaminobenzidine (polyDAB) have been determined at wavelengths of 450 nm and 480 nm, respectively, for quantitative histochemical analysis of phosphatase reactions. These values are essential for the conversion of

  20. Melanoidins extinction coefficient in the glucose/glycine Maillard reaction

    NARCIS (Netherlands)

    Martins, S.I.F.S.; Boekel, van M.A.J.S.

    2003-01-01

    Melanoidins (brown, nitrogenous polymers and co-polymers) are the final products of the Maillard reaction. The glucose/glycine melanoidins extinction coefficient was determined using C-14-labelled glucose at three different reaction conditions. The absorbance was measured at different wavelengths

  1. The empirical Gaia G-band extinction coefficient

    Science.gov (United States)

    Danielski, C.; Babusiaux, C.; Ruiz-Dern, L.; Sartoretti, P.; Arenou, F.

    2018-06-01

    Context. The first Gaia data release unlocked the access to photometric information for 1.1 billion sources in the G-band. Yet, given the high level of degeneracy between extinction and spectral energy distribution for large passbands such as the Gaia G-band, a correction for the interstellar reddening is needed in order to exploit Gaia data. Aims: The purpose of this manuscript is to provide the empirical estimation of the Gaia G-band extinction coefficient kG for both the red giants and main sequence stars in order to be able to exploit the first data release DR1. Methods: We selected two samples of single stars: one for the red giants and one for the main sequence. Both samples are the result of a cross-match between Gaia DR1 and 2MASS catalogues; they consist of high-quality photometry in the G-, J- and KS-bands. These samples were complemented by temperature and metallicity information retrieved from APOGEE DR13 and LAMOST DR2 surveys, respectively. We implemented a Markov chain Monte Carlo method where we used (G - KS)0 versus Teff and (J - KS)0 versus (G - KS)0, calibration relations to estimate the extinction coefficient kG and we quantify its corresponding confidence interval via bootstrap resampling. We tested our method on samples of red giants and main sequence stars, finding consistent solutions. Results: We present here the determination of the Gaia extinction coefficient through a completely empirical method. Furthermore we provide the scientific community with a formula for measuring the extinction coefficient as a function of stellar effective temperature, the intrinsic colour (G - KS)0, and absorption.

  2. The determination of extinction coefficient of CuInS2, and ZnCuInS3 multinary nanocrystals.

    Science.gov (United States)

    Qin, Lei; Li, Dongze; Zhang, Zhuolei; Wang, Kefei; Ding, Hong; Xie, Renguo; Yang, Wensheng

    2012-10-21

    A pioneering work for determining the extinction coefficient of colloidal semiconductor nanocrystals (NCs) has been cited over 1500 times (W. Yu, W. Guo, X. G. Peng, Chem. Mater., 2003, 15, 2854-2860), indicating the importance of calculating NC concentration for further research and applications. In this study, the size-dependent nature of the molar extinction coefficient of "greener" CuInS(2) and ZnCuInS(3) NCs with emission covering the whole visible to near infrared (NIR) is presented. With the increase of NC size, the resulting quantitative values of the extinction coefficients of ternary CuInS(2) and quaternary ZnCuInS(3) NCs are found to follow a power function with exponents of 2.1 and 2.5, respectively. Obviously, a larger value of extinction coefficient is observed in quaternary NCs for the same size of particles. The difference of the extinction coefficient from both samples is clearly demonstrated due to incorporating ZnS with a much larger extinction coefficient into CuInS(2) NCs.

  3. Turbid Media Extinction Coefficient for Near-Infrared Laser Radiation

    International Nuclear Information System (INIS)

    Dreischuh, T; Gurdev, L; Vankov, O; Stoyanov, D; Avramov, L

    2015-01-01

    In this work, extended investigations are performed of the extinction coefficient of Intralipid-20% dilutions in distilled water depending on the Intralipid concentration, for laser radiation wavelengths in the red and near-infrared regions covering the so-called tissue optical window. The extinction is measured by using an approach we have developed recently based on the features of the spatial intensity distribution of laser-radiation beams propagating through semi-infinite turbid media. The measurements are conducted using separately two dilution- containing plexiglass boxes of different sizes and volumes, in order to prove the appropriateness of the assumption of semi-infinite turbid medium. The experimental results for the extinction are in agreement with our previous results and with empiric formulae found by other authors concerning the wavelength dependence of the scattering coefficient of Intralipid – 10% and Intralipid – 20%. They are also in agreement with known data of the water absorptance. It is estimated as well that the wavelengths around 1320 nm would be advantageous for deep harmless sensing and diagnostics of tissues

  4. Experimental Determination of Infrared Extinction Coefficients of Interplanetary Dust Particles

    Science.gov (United States)

    Spann, J. F., Jr.; Abbas, M. M.

    1998-01-01

    This technique is based on irradiating a single isolated charged dust particle suspended in balance by an electric field, and measuring the scattered radiation as a function of angle. The observed scattered intensity profile at a specific wavelength obtained for a dust particle of known composition is compared with Mie theory calculations, and the variable parameters relating to the particle size and complex refractive index are adjusted for a best fit between the two profiles. This leads to a simultaneous determination of the particle radius, the complex refractive index, and the scattering and extinction coefficients. The results of these experiments can be utilized to examine the IRAS and DIRBE (Diffuse Infrared Background Experiment) infrared data sets in order to determine the dust particle physical characteristics and distributions by using infrared models and inversion techniques. This technique may also be employed for investigation of the rotational bursting phenomena whereby large size cosmic and interplanetary particles are believed to fragment into smaller dust particles.

  5. HIRDLS/Aura Level 3 Extinction at 12.1 Microns Zonal Fourier Coefficients V007

    Data.gov (United States)

    National Aeronautics and Space Administration — The "HIRDLS/Aura Level 3 Extinction at 12.1 Microns Zonal Fourier Coefficients" version 7 data product (H3ZFC12MEXT) contains the entire mission (~3 years) of HIRDLS...

  6. Far infrared extinction coefficients of minerals of interest for astronomical observations

    International Nuclear Information System (INIS)

    Hasegawa, H.

    1984-01-01

    Far infrared extinction coefficients of mineral grains of interest for astronomical observations have been measured. The measured mineral species are: amorphous carbon, high temperature magnesium silicates, hydrous silicates, iron oxides, and amorphous silicates. (author)

  7. Osmotic coefficients and apparent molar volumes of 1-hexyl-3-methylimidazolium trifluoromethanesulfonate ionic liquid in alcohols

    International Nuclear Information System (INIS)

    González, Emilio J.; Calvar, Noelia; Macedo, Eugénia A.

    2014-01-01

    Highlights: • Physical and osmotic properties of [HMim][TfO] in alcohols are reported. • Apparent molar properties and osmotic coefficients were obtained. • Apparent molar volumes were fitted using a Redlich–Meyer type equation. • The osmotic coefficients were modeled with the Extended Pitzer and the MNRTL models. -- Abstract: In this work, density for the binary mixtures of 1-hexyl-3-methylimidazolium trifluoromethanesulfonate in alcohols (1-propanol, or 2-propanol, or 1-butanol, or 2-butanol, or 1-pentanol) was measured at T = 323.15 K and atmospheric pressure. From this property, the corresponding apparent molar volumes were calculated and fitted to a Redlich–Meyer type equation. For these mixtures, the osmotic and activity coefficients, and vapor pressures of these binary systems were also determined at the same temperature using the vapor pressure osmometry technique. The experimental osmotic coefficients were modeled by the Extended Pitzer model of Archer. The parameters obtained in this correlation were used to calculate the mean molal activity coefficients and the excess Gibbs free energy for the studied mixtures

  8. An Improved Method of Predicting Extinction Coefficients for the Determination of Protein Concentration.

    Science.gov (United States)

    Hilario, Eric C; Stern, Alan; Wang, Charlie H; Vargas, Yenny W; Morgan, Charles J; Swartz, Trevor E; Patapoff, Thomas W

    2017-01-01

    Concentration determination is an important method of protein characterization required in the development of protein therapeutics. There are many known methods for determining the concentration of a protein solution, but the easiest to implement in a manufacturing setting is absorption spectroscopy in the ultraviolet region. For typical proteins composed of the standard amino acids, absorption at wavelengths near 280 nm is due to the three amino acid chromophores tryptophan, tyrosine, and phenylalanine in addition to a contribution from disulfide bonds. According to the Beer-Lambert law, absorbance is proportional to concentration and path length, with the proportionality constant being the extinction coefficient. Typically the extinction coefficient of proteins is experimentally determined by measuring a solution absorbance then experimentally determining the concentration, a measurement with some inherent variability depending on the method used. In this study, extinction coefficients were calculated based on the measured absorbance of model compounds of the four amino acid chromophores. These calculated values for an unfolded protein were then compared with an experimental concentration determination based on enzymatic digestion of proteins. The experimentally determined extinction coefficient for the native proteins was consistently found to be 1.05 times the calculated value for the unfolded proteins for a wide range of proteins with good accuracy and precision under well-controlled experimental conditions. The value of 1.05 times the calculated value was termed the predicted extinction coefficient. Statistical analysis shows that the differences between predicted and experimentally determined coefficients are scattered randomly, indicating no systematic bias between the values among the proteins measured. The predicted extinction coefficient was found to be accurate and not subject to the inherent variability of experimental methods. We propose the use of a

  9. Retrieval method of aerosol extinction coefficient profile by an integral lidar system and case study

    Science.gov (United States)

    Shan, Huihui; Zhang, Hui; Liu, Junjian; Wang, Shenhao; Ma, Xiaomin; Zhang, Lianqing; Liu, Dong; Xie, Chenbo; Tao, Zongming

    2018-02-01

    Aerosol extinction coefficient profile is an essential parameter for atmospheric radiation model. But it is difficult to get the full aerosol extinction profile from the ground to the tropopause especially in near ground precisely using backscattering lidar. A combined measurement of side-scattering, backscattering and Raman-scattering lidar is proposed to retrieve the aerosol extinction coefficient profile from the surface to the tropopause which covered a dynamic range of 5 orders. The side-scattering technique solves the dead zone and the overlap problem caused by the traditional lidar in the near range. Using the Raman-scattering the aerosol lidar ratio (extinction to backscatter ratio) can be obtained. The cases studies in this paper show the proposed method is reasonable and feasible.

  10. Small-scale Scheimpflug lidar for aerosol extinction coefficient and vertical atmospheric transmittance detection.

    Science.gov (United States)

    Sun, Guodong; Qin, Laian; Hou, Zaihong; Jing, Xu; He, Feng; Tan, Fengfu; Zhang, Silong

    2018-03-19

    In this paper, a new prototypical Scheimpflug lidar capable of detecting the aerosol extinction coefficient and vertical atmospheric transmittance at 1 km above the ground is described. The lidar system operates at 532 nm and can be used to detect aerosol extinction coefficients throughout an entire day. Then, the vertical atmospheric transmittance can be determined from the extinction coefficients with the equation of numerical integration in this area. CCD flat fielding of the image data is used to mitigate the effects of pixel sensitivity variation. An efficient method of two-dimensional wavelet transform according to a local threshold value has been proposed to reduce the Gaussian white noise in the lidar signal. Furthermore, a new iteration method of backscattering ratio based on genetic algorithm is presented to calculate the aerosol extinction coefficient and vertical atmospheric transmittance. Some simulations are performed to reduce the different levels of noise in the simulated signal in order to test the precision of the de-noising method and inversion algorithm. The simulation result shows that the root-mean-square errors of extinction coefficients are all less than 0.02 km -1 , and that the relative errors of the atmospheric transmittance between the model and inversion data are below 0.56% for all cases. The feasibility of the instrument and the inversion algorithm have also been verified by an optical experiment. The average relative errors of aerosol extinction coefficients between the Scheimpflug lidar and the conventional backscattering elastic lidar are 3.54% and 2.79% in the full overlap heights of two time points, respectively. This work opens up new possibilities of using a small-scale Scheimpflug lidar system for the remote sensing of atmospheric aerosols.

  11. Quantitative Analysis of Isolated Single-Wall Carbon Nanotubes with Their Molar Absorbance Coefficients

    Directory of Open Access Journals (Sweden)

    Shota Kuwahara

    2014-01-01

    Full Text Available The molar absorbance coefficients of metallic, semiconducting, and (6,5 chirality enriched single-wall carbon nanotubes were evaluated by a spray technique combined with atomic force microscopy. Single-wall carbon nanotubes with isolated and a single predominant electronic type were obtained by using the density-gradient ultracentrifugation technique. In the visible region, all coefficients had similar values around 2–5 × 109/mL mol−1 cm−1, independent of their diameter distribution and the electronic types of single-wall carbon nanotubes, and the εS22/εM11  and εS11/εM11 were estimated to be 1.0 and 4.0, respectively. The coefficient strongly depends on the length of single-wall carbon nanotubes, independent of their electronic types and chirality.

  12. Three-dimensional measurement of the local extinction coefficient in a dense spray

    International Nuclear Information System (INIS)

    Wellander, Rikard; Berrocal, Edouard; Kristensson, Elias; Richter, Mattias; Aldén, Marcus

    2011-01-01

    Laser extinction, signal attenuation and multiple scattering are the three main phenomena limiting qualitative and quantitative measurements in planar laser imaging of sprays. In this paper, a method is presented where structured laser illumination planar imaging is used to remove the signal contribution from multiply scattered light. Based on this technique, data from side scattering and transmission measurements are obtained simultaneously. An algorithm, compensating for signal attenuation and laser extinction, is further applied to calculate the local extinction coefficient. The method is first demonstrated on a cuvette containing a homogeneous solution of scattering particles with an extinction coefficient μ-bar e = 0.13 mm −1 . Finally the procedure is applied on an air-assisted water spray with a maximum optical depth of OD ∼ 3, where the position-dependent extinction coefficient is extracted within the probed volume. To the best of our knowledge, this paper demonstrates for the first time a method to measure the local μ-bar e within the three dimensions of an inhomogeneous scattering medium using laser sheet illumination, after suppression of the multiple light scattering intensity

  13. Atmospheric extinction coefficients and night sky brightness at the Xuyi Observation Station

    International Nuclear Information System (INIS)

    Zhang Hui-Hua; Liu Xiao-Wei; Zhang Hua-Wei; Xiang Mao-Sheng; Yuan Hai-Bo; Zhao Hai-Bin; Yao Jin-Sheng

    2013-01-01

    We present measurements of the optical broadband atmospheric extinction coefficients and the night sky brightness at the Xuyi Observation Station of Purple Mountain Observatory. The measurements are based on CCD imaging data taken in the Sloan Digital Sky Survey's g, r and i bands with the Xuyi 1.04/1.20 m Schmidt Telescope for the Xuyi Schmidt Telescope Photometric Survey of the Galactic Anti-center (XSTPS-GAC), the photometric part of the Digital Sky Survey of the Galactic Anti-center (DSS-GAC). The data were collected during more than 140 winter nights from 2009 to 2011. We find that the atmospheric extinction coefficients for the g, r and i bands are 0.69, 0.55 and 0.38 mag/airmass, respectively, based on observations taken on several photometric nights. The night sky brightness determined from images with good quality has median values of 21.7, 20.8 and 20.0 mag arcsec −2 and reaches 22.1, 21.2 and 20.4 mag arcsec −2 under the best observing conditions for the g, r and i bands, respectively. The relatively large extinction coefficients compared with other good astronomical observing sites are mainly due to the relatively low elevation (i.e. 180 m) and high humidity at the station.

  14. Precise determination of protein extinction coefficients under native and denaturing conditions using SV-AUC.

    Science.gov (United States)

    Hoffmann, Andreas; Grassl, Kerstin; Gommert, Janine; Schlesak, Christian; Bepperling, Alexander

    2018-04-17

    The accurate determination of protein concentration is an important though non-trivial task during the development of a biopharmaceutical. The fundamental prerequisite for this is the availability of an accurate extinction coefficient. Common approaches for the determination of an extinction coefficient for a given protein are either based on the theoretical prediction utilizing the amino acid sequence or the photometric determination combined with a measurement of absolute protein concentration. Here, we report on an improved SV-AUC based method utilizing an analytical ultracentrifuge equipped with absorbance and Rayleigh interference optics. Global fitting of datasets helped to overcome some of the obstacles encountered with the traditional method employing synthetic boundary cells. Careful calculation of dn/dc values taking glycosylation and solvent composition into account allowed the determination of the extinction coefficients of monoclonal antibodies and an Fc-fusion protein under native as well as under denaturing conditions. An intra-assay precision of 0.9% and an accuracy of 1.8% compared to the theoretical value was achieved for monoclonal antibodies. Due to the large number of data points of a single dataset, no meaningful difference between the ProteomeLab XL-I and the new Optima AUC platform could be observed. Thus, the AUC-based approach offers a precise, convenient and versatile alternative to conventional methods like total amino acid analysis (AAA).

  15. Determination of extinction coefficients of human hemoglobin in various redox states.

    Science.gov (United States)

    Meng, Fantao; Alayash, Abdu I

    2017-03-15

    The role of hemoglobin (Hb) redox forms in tissue and organ toxicities remain ambiguous despite the well-documented contribution of Hb redox reactivity to cellular and subcellular oxidative changes. Moreover, several recent studies, in which Hb toxicity were investigated, have shown conflicting outcomes. Uncertainties over the potential role of these species may in part be due to the protein preparation method of choice, the use of published extinction coefficients and the lack of suitable controls for Hb oxidation and heme loss. Highly purified and well characterized redox forms of human Hb were used in this study and the extinction coefficients of each Hb species (ferrous/oxy, ferric/met and ferryl) were determined. A new set of equations were established to improve accuracy in determining the transient ferryl Hb species. Additionally, heme concentrations in solutions and in human plasma were determined using a novel reversed phase HPLC method in conjugation with our photometric measurements. The use of more accurate redox-specific extinction coefficients and method calculations will be an invaluable tool for both in vitro and in vivo experiments aimed at determining the role of Hb-mediated vascular pathology in hemolytic anemias and when Hb is used as oxygen therapeutics. Published by Elsevier Inc.

  16. Parameterization of the Extinction Coefficient in Ice and Mixed-Phase Arctic Clouds during the ISDAC Field Campaign

    Energy Technology Data Exchange (ETDEWEB)

    Korolev, A; Shashkov, A; Barker, H

    2012-03-06

    This report documents the history of attempts to directly measure cloud extinction, the current measurement device known as the Cloud Extinction Probe (CEP), specific problems with direct measurement of extinction coefficient, and the attempts made here to address these problems. Extinction coefficient is one of the fundamental microphysical parameters characterizing bulk properties of clouds. Knowledge of extinction coefficient is of crucial importance for radiative transfer calculations in weather prediction and climate models given that Earth's radiation budget (ERB) is modulated much by clouds. In order for a large-scale model to properly account for ERB and perturbations to it, it must ultimately be able to simulate cloud extinction coefficient well. In turn this requires adequate and simultaneous simulation of profiles of cloud water content and particle habit and size. Similarly, remote inference of cloud properties requires assumptions to be made about cloud phase and associated single-scattering properties, of which extinction coefficient is crucial. Hence, extinction coefficient plays an important role in both application and validation of methods for remote inference of cloud properties from data obtained from both satellite and surface sensors (e.g., Barker et al. 2008). While estimation of extinction coefficient within large-scale models is relatively straightforward for pure water droplets, thanks to Mie theory, mixed-phase and ice clouds still present problems. This is because of the myriad forms and sizes that crystals can achieve, each having their own unique extinction properties. For the foreseeable future, large-scale models will have to be content with diagnostic parametrization of crystal size and type. However, before they are able to provide satisfactory values needed for calculation of radiative transfer, they require the intermediate step of assigning single-scattering properties to particles. The most basic of these is extinction

  17. New naphthalene polyimide with unusual molar absorption coefficient and excited state properties: Synthesis, photophysics and electrochemistry

    Energy Technology Data Exchange (ETDEWEB)

    Ozser, Mustafa E. [Girne American University, Faculty of Engineering and Architecture, Department of Industrial Engineering, Girne, North Cyprus (Cyprus); Yucekan, Ilke; Bodapati, Jagadeesh B. [Eastern Mediterranean University, Faculty of Arts and Sciences, Department of Chemistry, Famagusta, North Cyprus (Cyprus); Icil, Huriye, E-mail: huriye.icil@emu.edu.tr [Eastern Mediterranean University, Faculty of Arts and Sciences, Department of Chemistry, Famagusta, North Cyprus (Cyprus)

    2013-11-15

    A high molecular weight 1,4,5,8-naphthalene polyimide (ENPI) by one-step polycondensation mechanism and for comparison its monomeric diimide (ENDI) were synthesized; the photophysical and electrochemical properties were studied in detail for ENPI. Monomer has shown unusual insolubility so that the characterization proven to be difficult, whereas ENPI has shown better solubility. The molecular weight data obtained by GPC for the polymer were M{sub n}=8240 and M{sub w}=34,000 g mol{sup −1} respectively with a polydispersity of 4.13. The polyimide exhibited outstandingly high molar absorption coefficients as 599,000, 1,021,000, and 972,700 M{sup −1} cm{sup −1}, which is first time reported in literature for the characteristic 0–2, 0–1, and 0–0 electronic transitions, respectively. ENPI showed concentration dependent and red shifted excimer emission in 1,1,2,2-tetrachloroethane (TCE). The polymer has undergone multielectron reductions in CHCl{sub 3} solution below 100 mV s{sup −1} scan rates which merged into two reversible one-electron reduction peaks at higher scan rates. In solid-state, similar scan rate dependent reduction peaks were noticed. The LUMO, HOMO and optical band gap values obtained for ENPI were −3.73, −6.91, and 3.18 eV respectively. ENDI polymer with striking features has great potential as new sensitizer for efficient dye sensitized organic cells. Highlights: • A high molecular weight naphthalene polyimide was synthesized (M{sub w}=34,000 g mol{sup −1}). • The oligoether polyimide exhibited outstanding molar absorptivity (972,700 M{sup −1} cm{sup −1}). • A red shifted excimer emission has been observed. • The polymer has undergone multielectron reductions.

  18. Studying the extinction coefficient due to aerosol particles at different spectral bands in some regions at great Cairo

    International Nuclear Information System (INIS)

    Shaltout, M.A. Mosalam; Tadros, M.T.Y.; El-Metwally, M.

    2000-01-01

    Extinction coefficient due to aerosol has been estimated by Pyrheliometric and Gorgie type Actinometric measurements in the industrial, urban areas and compared with agricultural areas. The measurements distributed over one year from June 1992 to May 1993 were made under clear sky for five spectral bands. The results show two maxima in hot wet and spring months and minimum in winter months, but there is a fluctuation in urban area. Diurnal variations show maximum at noon especially in the industrial area. Level of extinction coefficient in the industrial and urban area is greater that that of the agricultural area, except for hot wet months is due to the increase of water vapor content in agricultural area. Spectral distribution of the extinction coefficient decreases monotonically with wavelength. Size of particles in industrial area is greater than in urban and agricultural areas. The temperature and water vapor content have important rules in increasing the extinction coefficient of aerosols. (Author)

  19. Evaluation of the Extinction Coefficient, Radiation Absorption and Use Efficiency of Saffron (Crocus sativus L.

    Directory of Open Access Journals (Sweden)

    Seyyedeh Maliheh Mirhashemi

    2015-10-01

    Full Text Available Leaf area index, light extinction coefficient and radiation use efficiency are important eco-physiological characteristics for realization of crops growth, development and radiation absorption. In order to determine the leaf area index (LAI, light extinction coefficient (K and radiation use efficiency (RUE of saffron during the first and second growing seasons, four experiments were started in 2011 and ended in 2014, at the Research Farm of the Agriculture Faculty, the Ferdowsi University of Mashhad, Iran. Saffron corms with weights between 13 to15 g and density of 50 plant.m2 were cultivated in 2011 and 2012. In all experimental years during the growing season, crop sampling was taken for required measurements including the leaf area index and shoot dry weight of saffron once every 14 days. The results showed that by increasing the age of saffron from 1 year to two years, the maximum LAI of saffron increased from 0.33 to 1.81, and light extinction coefficient decreased from 1.20 to 0.54. The increasing trend of LAI was coincident with fraction of absorbed radiation for all four years of the experiment. In the first and the second growing seasons, the amount of fraction of absorbed radiation gradually increased with increasing LAI and at 1083 and 1034 GDD reached its maximum value, respectively. In saffron farms when the plant was one year old and two years old, the mean value of RUE was 0.68 and 1.73 g.MJ-1 PAR, respectively. These results indicate that by increasing the saffron age and LAI, the value of K decreases and consequently radiation absorption and use efficiency will‎ increase.

  20. Row spacing effects on light extinction coefficients of corn, sorghum, soybean, and sunflower

    International Nuclear Information System (INIS)

    Flénet, F.; Kiniry, J.R.; Board, J.E.; Westgate, M.E.; Reicosky, D.C.

    1996-01-01

    In many crop models, light intercepted by a canopy (IPAR) is calculated from a Beer's Law equation: IPAR = PAR x [1- exp(-k x LAI)], where k is the extinction coefficient, PAR the photosynthetically active radiation, and LAI the leaf area index. The first objective of this study was to investigate the effect of row spacing on k for corn (Zea mays L.), sorghum [Sorghum bicolor (L.) Moench], soybean [Glycine max (L.) Merr.], and sunflower (Helianthus annuus L.) to provide information for modeling. Data from literature and from an experiment conducted at Temple, TX, were evaluated. The second objective was to investigate effects of time of day and stage of crop development on k for different row spacings. Seeds of all four species were sown in rows 0.35, 0.66, or 1.00 m apart. Measurements of canopy light interception were taken near solar noon on two dates before anthesis. At anthesis, extinction coefficients were determined at 0845, 1015, and 1145 h (solar time). The extinction coefficient showed a linear decrease as row spacing increased. For each crop, the effect of row spacing on k was described by one linear regression for most data. Stage of crop development and stage of development x row spacing interaction did not significantly affect k during the period of measurements. The effect of time of day was significant for all four crops, and the time of day x row spacing interaction was significant for soybean and sunflower. Thus, modeling light interception for different row spacings should account for these effects

  1. The functional correlation between rainfall rate and extinction coefficient for frequencies from 3 to 10 GHz

    Science.gov (United States)

    Jameson, A. R.

    1990-01-01

    The relationship between the rainfall rate (R) obtained from radiometric brightness temperatures and the extinction coefficient (k sub e) is investigated by computing the values of k sub e over a wide range of rainfall rates, for frequencies from 3 to 25 GHz. The results show that the strength of the relation between the R and the k sub e values exhibits considerable variation for frequencies at this range. Practical suggestions are made concerning the selection of particular frequencies for rain measurements to minimize the error in R determinations.

  2. Retrieval method of aerosol extinction coefficient profile based on backscattering, side-scattering and Raman-scattering lidar

    Science.gov (United States)

    Shan, Huihui; Zhang, Hui; Liu, Junjian; Tao, Zongming; Wang, Shenhao; Ma, Xiaomin; Zhou, Pucheng; Yao, Ling; Liu, Dong; Xie, Chenbo; Wang, Yingjian

    2018-03-01

    Aerosol extinction coefficient profile is an essential parameter for atmospheric radiation model. It is difficult to get higher signal to noise ratio (SNR) of backscattering lidar from the ground to the tropopause especially in near range. Higher SNR problem can be solved by combining side-scattering and backscattering lidar. Using Raman-scattering lidar, aerosol extinction to backscatter ratio (lidar ratio) can be got. Based on side-scattering, backscattering and Raman-scattering lidar system, aerosol extinction coefficient is retrieved precisely from the earth's surface to the tropopause. Case studies show this method is reasonable and feasible.

  3. Research on bimodal particle extinction coefficient during Brownian coagulation and condensation for the entire particle size regime

    International Nuclear Information System (INIS)

    Tang Hong; Lin Jianzhong

    2011-01-01

    The extinction coefficient of atmospheric aerosol particles influences the earth’s radiation balance directly or indirectly, and it can be determined by the scattering and absorption characteristics of aerosol particles. The problem of estimating the change of extinction coefficient due to time evolution of bimodal particle size distribution is studied, and two improved methods for calculating the Brownian coagulation coefficient and the condensation growth rate are proposed, respectively. Through the improved method based on Otto kernel, the Brownian coagulation coefficient can be expressed simply in powers of particle volume for the entire particle size regime based on the fitted polynomials of the mean enhancement function. Meanwhile, the improved method based on Fuchs–Sutugin kernel is developed to obtain the condensation growth rate for the entire particle size regime. And then, the change of the overall extinction coefficient of bimodal distributions undergoing Brownian coagulation and condensation can be estimated comprehensively for the entire particle size regime. Simulation experiments indicate that the extinction coefficients obtained with the improved methods coincide fairly well with the true values, which provide a simple, reliable, and general method to estimate the change of extinction coefficient for the entire particle size regime during the bimodal particle dynamic processes.

  4. Effect of Nitrogen Fertilizer on Light Interception and Light Extinction Coefficient in Different Wheat Cultivars

    Directory of Open Access Journals (Sweden)

    F Samadiyan

    2016-07-01

    Full Text Available Introduction Wheat (Triticum aestivum is a cereal grain, originated from the levant region of the near east and Ethiopian highlands, currently cultivated worldwide. Light extinction coefficient K is a coefficient that represents the amount of light reduced by the plant. Light or radiation extinction coefficient is a concept that expresses the light penetration decrease into the canopy in the way the upper leaves of the canopy with less angles have lower amount of K in comparison with the horizontal leaves. Green et al., (2003 stated that nitrogen fertilizer increased light absorption by plant leaves; and affects the yield. The distribution patterns of nitrogen allocation in leaves are more exposed therefore photosynthesis rate per unit leaf area and canopy were optimized. Differences in canopy structure by the light extinction coefficient (k of the Act Lambert - Beer is described, along LAI differing due to different species and genotypes which are important factors in absorption and light use efficiency. This experiment was performed to evaluate the maximum light absorption and light extinction coefficient in different levels of nitrogen usage and wheat cultivars. Materials and Methods An experiment was conducted during 2011-2012 on a research farm of Islamic Azad University, Isfahan Branch, located in Khatoon Abad Village (northern latitude of 320 and 40´ and eastern longitude of 510 and 48´ with altitude of 1555 m above sea level. A split plot layout within randomized complete block design was used with three replications. Main plots were consisted in four levels of N fertilizer (0, 50, 100 and 150 kg ha-1 from an urea source in main plots and different cultivars of wheat included Pishtaz, Sepahan and SW-486 in sub plots. Planting was performed on 14 November 2011 and at a density of 400 plants per square meter. In order to strengthen the land and required elements for plant regarding soil test and treatments based on the test plan, the

  5. Determination of the particulate extinction-coefficient profile and the column-integrated lidar ratios using the backscatter-coefficient and optical-depth profiles

    Science.gov (United States)

    Vladimir A Kovalev; Wei Min Hao; Cyle Wold

    2007-01-01

    A new method is considered that can be used for inverting data obtained from a combined elastic-inelastic lidar or a high spectral resolution lidar operating in a one-directional mode, or an elastic lidar operating in a multiangle mode. The particulate extinction coefficient is retrieved from the simultaneously measured profiles of the particulate backscatter...

  6. Variation of haemoglobin extinction coefficients can cause errors in the determination of haemoglobin concentration measured by near-infrared spectroscopy

    International Nuclear Information System (INIS)

    Kim, J G; Liu, H

    2007-01-01

    Near-infrared spectroscopy or imaging has been extensively applied to various biomedical applications since it can detect the concentrations of oxyhaemoglobin (HbO 2 ), deoxyhaemoglobin (Hb) and total haemoglobin (Hb total ) from deep tissues. To quantify concentrations of these haemoglobin derivatives, the extinction coefficient values of HbO 2 and Hb have to be employed. However, it was not well recognized among researchers that small differences in extinction coefficients could cause significant errors in quantifying the concentrations of haemoglobin derivatives. In this study, we derived equations to estimate errors of haemoglobin derivatives caused by the variation of haemoglobin extinction coefficients. To prove our error analysis, we performed experiments using liquid-tissue phantoms containing 1% Intralipid in a phosphate-buffered saline solution. The gas intervention of pure oxygen was given in the solution to examine the oxygenation changes in the phantom, and 3 mL of human blood was added twice to show the changes in [Hb total ]. The error calculation has shown that even a small variation (0.01 cm -1 mM -1 ) in extinction coefficients can produce appreciable relative errors in quantification of Δ[HbO 2 ], Δ[Hb] and Δ[Hb total ]. We have also observed that the error of Δ[Hb total ] is not always larger than those of Δ[HbO 2 ] and Δ[Hb]. This study concludes that we need to be aware of any variation in haemoglobin extinction coefficients, which could result from changes in temperature, and to utilize corresponding animal's haemoglobin extinction coefficients for the animal experiments, in order to obtain more accurate values of Δ[HbO 2 ], Δ[Hb] and Δ[Hb total ] from in vivo tissue measurements

  7. Variation of haemoglobin extinction coefficients can cause errors in the determination of haemoglobin concentration measured by near-infrared spectroscopy

    Science.gov (United States)

    Kim, J. G.; Liu, H.

    2007-10-01

    Near-infrared spectroscopy or imaging has been extensively applied to various biomedical applications since it can detect the concentrations of oxyhaemoglobin (HbO2), deoxyhaemoglobin (Hb) and total haemoglobin (Hbtotal) from deep tissues. To quantify concentrations of these haemoglobin derivatives, the extinction coefficient values of HbO2 and Hb have to be employed. However, it was not well recognized among researchers that small differences in extinction coefficients could cause significant errors in quantifying the concentrations of haemoglobin derivatives. In this study, we derived equations to estimate errors of haemoglobin derivatives caused by the variation of haemoglobin extinction coefficients. To prove our error analysis, we performed experiments using liquid-tissue phantoms containing 1% Intralipid in a phosphate-buffered saline solution. The gas intervention of pure oxygen was given in the solution to examine the oxygenation changes in the phantom, and 3 mL of human blood was added twice to show the changes in [Hbtotal]. The error calculation has shown that even a small variation (0.01 cm-1 mM-1) in extinction coefficients can produce appreciable relative errors in quantification of Δ[HbO2], Δ[Hb] and Δ[Hbtotal]. We have also observed that the error of Δ[Hbtotal] is not always larger than those of Δ[HbO2] and Δ[Hb]. This study concludes that we need to be aware of any variation in haemoglobin extinction coefficients, which could result from changes in temperature, and to utilize corresponding animal's haemoglobin extinction coefficients for the animal experiments, in order to obtain more accurate values of Δ[HbO2], Δ[Hb] and Δ[Hbtotal] from in vivo tissue measurements.

  8. Variation of haemoglobin extinction coefficients can cause errors in the determination of haemoglobin concentration measured by near-infrared spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Kim, J G; Liu, H [Joint Graduate Program in Biomedical Engineering, University of Texas at Arlington/University of Texas Southwestern Medical Center at Dallas, Arlington, TX 76019 (United States)

    2007-10-21

    Near-infrared spectroscopy or imaging has been extensively applied to various biomedical applications since it can detect the concentrations of oxyhaemoglobin (HbO{sub 2}), deoxyhaemoglobin (Hb) and total haemoglobin (Hb{sub total}) from deep tissues. To quantify concentrations of these haemoglobin derivatives, the extinction coefficient values of HbO{sub 2} and Hb have to be employed. However, it was not well recognized among researchers that small differences in extinction coefficients could cause significant errors in quantifying the concentrations of haemoglobin derivatives. In this study, we derived equations to estimate errors of haemoglobin derivatives caused by the variation of haemoglobin extinction coefficients. To prove our error analysis, we performed experiments using liquid-tissue phantoms containing 1% Intralipid in a phosphate-buffered saline solution. The gas intervention of pure oxygen was given in the solution to examine the oxygenation changes in the phantom, and 3 mL of human blood was added twice to show the changes in [Hb{sub total}]. The error calculation has shown that even a small variation (0.01 cm{sup -1} mM{sup -1}) in extinction coefficients can produce appreciable relative errors in quantification of {delta}[HbO{sub 2}], {delta}[Hb] and {delta}[Hb{sub total}]. We have also observed that the error of {delta}[Hb{sub total}] is not always larger than those of {delta}[HbO{sub 2}] and {delta}[Hb]. This study concludes that we need to be aware of any variation in haemoglobin extinction coefficients, which could result from changes in temperature, and to utilize corresponding animal's haemoglobin extinction coefficients for the animal experiments, in order to obtain more accurate values of {delta}[HbO{sub 2}], {delta}[Hb] and {delta}[Hb{sub total}] from in vivo tissue measurements.

  9. Toward a Combined SAGE II-HALOE Aerosol Climatology: An Evaluation of HALOE Version 19 Stratospheric Aerosol Extinction Coefficient Observations

    Science.gov (United States)

    Thomason, L. W.

    2012-01-01

    Herein, the Halogen Occultation Experiment (HALOE) aerosol extinction coefficient data is evaluated in the low aerosol loading period after 1996 as the first necessary step in a process that will eventually allow the production of a combined HALOE/SAGE II (Stratospheric Aerosol and Gas Experiment) aerosol climatology of derived aerosol products including surface area density. Based on these analyses, it is demonstrated that HALOE's 3.46 microns is of good quality above 19 km and suitable for scientific applications above that altitude. However, it is increasingly suspect at lower altitudes and should not be used below 17 km under any circumstances after 1996. The 3.40 microns is biased by about 10% throughout the lower stratosphere due to the failure to clear NO2 but otherwise appears to be a high quality product down to 15 km. The 2.45 and 5.26 micron aerosol extinction coefficient measurements are clearly biased and should not be used for scientific applications after the most intense parts of the Pinatubo period. Many of the issues in the aerosol data appear to be related to either the failure to clear some interfering gas species or doing so poorly. For instance, it is clear that the 3.40micronaerosol extinction coefficient measurements can be improved through the inclusion of an NO2 correction and could, in fact, end up as the highest quality overall HALOE aerosol extinction coefficient measurement. It also appears that the 2.45 and 5.26 micron channels may be improved by updating the Upper Atmosphere Pilot Database which is used as a resource for the removal of gas species otherwise not available from direct HALOE measurements. Finally, a simple model to demonstrate the promise of mixed visible/infrared aerosol extinction coefficient ensembles for the retrieval of bulk aerosol properties demonstrates that a combined HALOE/SAGE II aerosol climatology is feasible and may represent a substantial improvement over independently derived data sets.

  10. The Influence of Aerosol Hygroscopicity on Retrieving the Aerosol Extincting Coefficient from MPL Data

    Science.gov (United States)

    Zhao, G.; Zhao, C.

    2016-12-01

    Micro-pulse Lidar (MPL) measurements have been widely used to profile the ambient aerosol extincting coefficient(). Lidar Ratio (LR) ,which highly depends on the particle number size distribution (PNSD) and aerosol hygroscopicity, is the most important factor to retrieve the profile. A constant AOD constrained LR is usually used in current algorithms, which would lead to large bias when the relative humidity (RH) in the mixed layer is high. In this research, the influences of PNSD, aerosol hygroscopicity and RH profiles on the vertical variation of LR were investigated based on the datasets from field measurements in the North China Plain (NCP). Results show that LR can have an enhancement factor of more than 120% when the RH reaches to 92%. A new algorithm of retrieving the profile is proposed based on the variation of LR due to aerosol hygroscopicity. The magnitude and vertical structures of retrieved using this method can be significantly different to that of the fiexed LR method. The relative difference can reach up to 40% when the RH in the mixed layer is higher than 90% . Sensitivity studies show that RH profile and PNSD affect most on the retrieved by fiexed LR method. In view of this, a scheme of LR enhancement factor by RH is proposed in the NCP. The relative differnce of the calculated between using this scheme and the new algorithm with the variable LR can be less than 10%.

  11. Determination of a refractive index and an extinction coefficient of standard production of CVD-graphene.

    Science.gov (United States)

    Ochoa-Martínez, Efraín; Gabás, Mercedes; Barrutia, Laura; Pesquera, Amaia; Centeno, Alba; Palanco, Santiago; Zurutuza, Amaia; Algora, Carlos

    2015-01-28

    The refractive index and extinction coefficient of chemical vapour deposition grown graphene are determined by ellipsometry analysis. Graphene films were grown on copper substrates and transferred as both monolayers and bilayers onto SiO2/Si substrates by using standard manufacturing procedures. The chemical nature and thickness of residual debris formed after the transfer process were elucidated using photoelectron spectroscopy. The real layered structure so deduced has been used instead of the nominal one as the input in the ellipsometry analysis of monolayer and bilayer graphene, transferred onto both native and thermal silicon oxide. The effect of these contamination layers on the optical properties of the stacked structure is noticeable both in the visible and the ultraviolet spectral regions, thus masking the graphene optical response. Finally, the use of heat treatment under a nitrogen atmosphere of the graphene-based stacked structures, as a method to reduce the water content of the sample, and its effect on the optical response of both graphene and the residual debris layer are presented. The Lorentz-Drude model proposed for the optical response of graphene fits fairly well the experimental ellipsometric data for all the analysed graphene-based stacked structures.

  12. Octanol-Water Partition Coefficient from 3D-RISM-KH Molecular Theory of Solvation with Partial Molar Volume Correction.

    Science.gov (United States)

    Huang, WenJuan; Blinov, Nikolay; Kovalenko, Andriy

    2015-04-30

    The octanol-water partition coefficient is an important physical-chemical characteristic widely used to describe hydrophobic/hydrophilic properties of chemical compounds. The partition coefficient is related to the transfer free energy of a compound from water to octanol. Here, we introduce a new protocol for prediction of the partition coefficient based on the statistical-mechanical, 3D-RISM-KH molecular theory of solvation. It was shown recently that with the compound-solvent correlation functions obtained from the 3D-RISM-KH molecular theory of solvation, the free energy functional supplemented with the correction linearly related to the partial molar volume obtained from the Kirkwood-Buff/3D-RISM theory, also called the "universal correction" (UC), provides accurate prediction of the hydration free energy of small compounds, compared to explicit solvent molecular dynamics [ Palmer , D. S. ; J. Phys.: Condens. Matter 2010 , 22 , 492101 ]. Here we report that with the UC reparametrized accordingly this theory also provides an excellent agreement with the experimental data for the solvation free energy in nonpolar solvent (1-octanol) and so accurately predicts the octanol-water partition coefficient. The performance of the Kovalenko-Hirata (KH) and Gaussian fluctuation (GF) functionals of the solvation free energy, with and without UC, is tested on a large library of small compounds with diverse functional groups. The best agreement with the experimental data for octanol-water partition coefficients is obtained with the KH-UC solvation free energy functional.

  13. Evaluating Nighttime CALIOP 0.532 micron Aerosol Optical Depth and Extinction Coefficient Retrievals

    Science.gov (United States)

    Campbell, J. R.; Tackett, J. L.; Reid, J. S.; Zhang, J.; Curtis, C. A.; Hyer, E. J.; Sessions, W. R.; Westphal, D. L.; Prospero, J. M.; Welton, E. J.; hide

    2012-01-01

    NASA Cloud Aerosol Lidar with Orthogonal Polarization (CALIOP) Version 3.01 5-km nighttime 0.532 micron aerosol optical depth (AOD) datasets from 2007 are screened, averaged and evaluated at 1 deg X 1 deg resolution versus corresponding/co-incident 0.550 micron AOD derived using the US Navy Aerosol Analysis and Prediction System (NAAPS), featuring two-dimensional variational assimilation of quality-assured NASA Moderate Resolution Imaging Spectroradiometer (MODIS) and Multi-angle Imaging Spectroradiometer (MISR) AOD. In the absence of sunlight, since passive radiometric AOD retrievals rely overwhelmingly on scattered radiances, the model represents one of the few practical global estimates available from which to attempt such a validation. Daytime comparisons, though, provide useful context. Regional-mean CALIOP vertical profiles of night/day 0.532 micron extinction coefficient are compared with 0.523/0.532 micron ground-based lidar measurements to investigate representativeness and diurnal variability. In this analysis, mean nighttime CALIOP AOD are mostly lower than daytime (0.121 vs. 0.126 for all aggregated data points, and 0.099 vs. 0.102 when averaged globally per normalised 1 deg. X 1 deg. bin), though the relationship is reversed over land and coastal regions when the data are averaged per normalised bin (0.134/0.108 vs. 0140/0.112, respectively). Offsets assessed within single bins alone approach +/- 20 %. CALIOP AOD, both day and night, are higher than NAAPS over land (0.137 vs. 0.124) and equal over water (0.082 vs. 0.083) when averaged globally per normalised bin. However, for all data points inclusive, NAAPS exceeds CALIOP over land, coast and ocean, both day and night. Again, differences assessed within single bins approach 50% in extreme cases. Correlation between CALIOP and NAAPS AOD is comparable during both day and night. Higher correlation is found nearest the equator, both as a function of sample size and relative signal magnitudes inherent at

  14. Toward a combined SAGE II-HALOE aerosol climatology: an evaluation of HALOE version 19 stratospheric aerosol extinction coefficient observations

    Directory of Open Access Journals (Sweden)

    L. W. Thomason

    2012-09-01

    Full Text Available Herein, the Halogen Occultation Experiment (HALOE aerosol extinction coefficient data is evaluated in the low aerosol loading period after 1996 as the first necessary step in a process that will eventually allow the production of a combined HALOE/SAGE II (Stratospheric Aerosol and Gas Experiment aerosol climatology of derived aerosol products including surface area density. Based on these analyses, it is demonstrated that HALOE's 3.46 μm is of good quality above 19 km and suitable for scientific applications above that altitude. However, it is increasingly suspect at lower altitudes and should not be used below 17 km under any circumstances after 1996. The 3.40 μm is biased by about 10% throughout the lower stratosphere due to the failure to clear NO2 but otherwise appears to be a high quality product down to 15 km. The 2.45 and 5.26 μm aerosol extinction coefficient measurements are clearly biased and should not be used for scientific applications after the most intense parts of the Pinatubo period. Many of the issues in the aerosol data appear to be related to either the failure to clear some interfering gas species or doing so poorly. For instance, it is clear that the 3.40 μm aerosol extinction coefficient measurements can be improved through the inclusion of an NO2 correction and could, in fact, end up as the highest quality overall HALOE aerosol extinction coefficient measurement. It also appears that the 2.45 and 5.26 μm channels may be improved by updating the Upper Atmosphere Pilot Database which is used as a resource for the removal of gas species otherwise not available from direct HALOE measurements. Finally, a simple model to demonstrate the promise of mixed visible/infrared aerosol extinction coefficient ensembles for the retrieval of bulk aerosol properties demonstrates that a combined HALOE/SAGE II aerosol climatology is feasible and may represent a substantial improvement over independently derived

  15. Liquid phase PVTx properties of (water + tert-butanol) binary mixtures at temperatures from 278.15 to 323.15 K and pressures from 0.1 to 100 MPa. II. Molar isothermal compressions, molar isobaric expansions, molar thermal pressure coefficients, and internal pressure

    International Nuclear Information System (INIS)

    Egorov, Gennadiy I.; Makarov, Dmitriy M.; Kolker, Arkadiy M.

    2013-01-01

    Highlights: ► Molar isothermal compressions and molar isobaric expansions were evaluated. ► Coefficients of thermal pressure and internal pressure were obtained. ► Concentration dependences of coefficients under study display extremes. ► Temperature and pressure dependences of internal pressure of the mixture were linear. -- Abstract: Molar isothermal compressions, molar isobaric expansions, molar coefficients of thermal pressure, and internal pressure were calculated over the whole concentration range of {water (1) + tert-butanol (2)} mixture at pressures from 0.1 to 100 MPa and temperatures from 278.15 to 323.15 K. It was revealed that the extremes, observed on concentration dependences of molar isothermal compression K T,m and molar isobaric expansion E P,m of the mixture, became more pronounced with pressure growth and temperature lowering. Values of molar thermal pressure coefficients of the mixture sharply rose at compositions with small TBA mole fraction and then decreased practically linearly with the alcohol content increasing. Temperature and pressure dependences of the mixture internal pressure were almost linear, and at low TBA concentrations changed significantly from the dependences of water, tert-butanol and their mixtures at large alcohol content

  16. Improved prediction of octanol-water partition coefficients from liquid-solute water solubilities and molar volumes

    Science.gov (United States)

    Chiou, C.T.; Schmedding, D.W.; Manes, M.

    2005-01-01

    A volume-fraction-based solvent-water partition model for dilute solutes, in which the partition coefficient shows a dependence on solute molar volume (V??), is adapted to predict the octanol-water partition coefficient (K ow) from the liquid or supercooled-liquid solute water solubility (Sw), or vice versa. The established correlation is tested for a wide range of industrial compounds and pesticides (e.g., halogenated aliphatic hydrocarbons, alkylbenzenes, halogenated benzenes, ethers, esters, PAHs, PCBs, organochlorines, organophosphates, carbamates, and amidesureas-triazines), which comprise a total of 215 test compounds spanning about 10 orders of magnitude in Sw and 8.5 orders of magnitude in Kow. Except for phenols and alcohols, which require special considerations of the Kow data, the correlation predicts the Kow within 0.1 log units for most compounds, much independent of the compound type or the magnitude in K ow. With reliable Sw and V data for compounds of interest, the correlation provides an effective means for either predicting the unavailable log Kow values or verifying the reliability of the reported log Kow data. ?? 2005 American Chemical Society.

  17. Apparent molar volumes, isobaric expansion coefficients, and isentropic compressibilities, and their H/D isotope effects for some aqueous carbohydrate solutions

    International Nuclear Information System (INIS)

    Bernal, P.J.; Van Hook, W.A.

    1986-01-01

    The molar volumes, isobaric expansion coefficients, and isentropic compressibilities of solutions of a number of carbohydrates and their deuterated isomers were determined in H 2 O and D 2 O between 288.15 and 328.15 K and over a wide range of solute-to-solvent mole ratios. The results are discussed in terms of the specific hydration model. (author)

  18. Experimental Determination of the Molar Absorption Coefficient of n-Hexane Adsorbed on High-Silica Zeolites.

    Science.gov (United States)

    Gatti, Giorgio; Olivas Olivera, Diana F; Sacchetto, Vittoria; Cossi, Maurizio; Braschi, Ilaria; Marchese, Leonardo; Bisio, Chiara

    2017-09-06

    Determination of the molar absorption coefficients of the CH 3 bending mode at ν˜ =1380 cm -1 (ϵ 1380 ) of n-hexane adsorbed from the gas phase on two different dealuminated zeolites is derived by a combination of IR spectroscopy and microgravimetric analysis. High-silica zeolite Y (HSZ-Y) and zeolite ZSM-5 (with SiO 2 /Al 2 O 3 ratios of 200 and 280, respectively) with different textural and surface features are selected to evaluate the effect of the pore structure and architecture on the value of ϵ 1380 of the adsorbed n-hexane. Experimental data indicate that the molecule experiences a different adsorption environment inside zeolites; thus resulting in a significant change of the dipole moment and very different ϵ 1380 values: (0.278±0.018) cm μmol -1 for HSZ-Y and (0.491±0.032) cm μmol -1 for ZSM-5. Experimental data are also supported by computational modeling, which confirms the effect of different matrices on the IR absorption intensity. This study reveals that the use of probe molecules for quantitative measurements of surface sites has to be judiciously adopted, especially if adsorption occurs in the restricted spaces of microporous materials. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Cowpea, Common Bean And Mung Bean Radiation Use Efficiency, Light Extinction Coefficient And Radiation Interception In Double Cropping

    International Nuclear Information System (INIS)

    Alimadadi, A.; Rostamza, M.; Jahansooz, M.R.; Ahmadi, A.; Tavakol Afshari, R.

    2006-01-01

    Crop growth modeling for forecasting various plant's functions and their contribution to yield, is one of the ways to improve field management. This trial was set up to evaluate radiation use efficiency of mung bean, common bean and cowpea cultivars in a double cropping system. Field experiment was conducted at Research Farm of College of Agriculture, University of Tehran, Karaj. A 4-replicate group balanced block field experiment was set up. Results showed that the differences among three pulses were significant in terms of biomass (p0.05). Cowpea, producing 5876.8 Kg/ha, had the highest yield among the species used in this study. Comparison of grain yield observed in this experiment with mono crop yield potential, showed that cowpea, common bean and mung bean produced 40%, 37% and 58% of their mono crop grain yield potential, respectively. In the late vegetative growth period, cowpea, mung bean and common bean absorbed 90%, 33% and 36% of photosynthetic active radiation, respectively. There was a significant difference among pulses, in terms of their radiation use efficiency and light extinction coefficient (p0.05 and p0.01, respectively). Cowpea, common bean and mung bean had radiation use efficiencies of 0.84, 0.82 and 0.99, g/MJ and light extinction coefficients of 0.605, 0.344 and 0.458, respectively. Results indicated that in some cultivars, when K decreases and LAI increases, LUE might be increased twice

  20. Comparison of ambient aerosol extinction coefficients obtained from in-situ, MAX-DOAS and LIDAR measurements at Cabauw

    Directory of Open Access Journals (Sweden)

    P. Zieger

    2011-03-01

    Full Text Available In the field, aerosol in-situ measurements are often performed under dry conditions (relative humidity RH<30–40%. Since ambient aerosol particles experience hygroscopic growth at enhanced RH, their microphysical and optical properties – especially the aerosol light scattering – are also strongly dependent on RH. The knowledge of this RH effect is of crucial importance for climate forcing calculations or for the comparison of remote sensing with in-situ measurements. Here, we will present results from a four-month campaign which took place in summer 2009 in Cabauw, The Netherlands. The aerosol scattering coefficient σsp(λ was measured dry and at various, predefined RH conditions between 20 and 95% with a humidified nephelometer. The scattering enhancement factor f(RH,λ is the key parameter to describe the effect of RH on σsp(λ and is defined as σsp(RH,λ measured at a certain RH divided by the dry σsp(dry,λ. The measurement of f(RH,λ together with the dry absorption measurement (assumed not to change with RH allows the determination of the actual extinction coefficient σep(RH,λ at ambient RH. In addition, a wide range of other aerosol properties were measured in parallel. The measurements were used to characterize the effects of RH on the aerosol optical properties. A closure study showed the consistency of the aerosol in-situ measurements. Due to the large variability of air mass origin (and thus aerosol composition a simple parameterization of f(RH,λ could not be established. If f(RH,λ needs to be predicted, the chemical composition and size distribution need to be known. Measurements of four MAX-DOAS (multi-axis differential optical absorption spectroscopy instruments were used to retrieve vertical profiles of σep(λ. The values of the lowest layer were compared to the in-situ values after conversion of the latter ones to ambient

  1. Spectro-ellipsometric studies of sputtered amorphous Titanium dioxide thin films: simultaneous determination of refractive index, extinction coefficient, and void distribution

    CERN Document Server

    Lee, S I; Oh, S G

    1999-01-01

    Amorphous titanium dioxide thin films were deposited onto silicon substrates by using RF magnetron sputtering, and the index of refraction, the extinction coefficient, and the void distribution of these films were simultaneously determined from the analyses of there ellipsometric spectra. In particular, our novel strategy, which combines the merits of multi-sample fitting, the dual dispersion function, and grid search, was proven successful in determining optical constants over a wide energy range, including the energy region where the extinction coefficient was large. Moreover, we found that the void distribution was dependent on the deposition conditions, such as the sputtering power, the substrate temperature, and the substrate surface.

  2. Determination of refractive index, extinction coefficient and thickness of thin films by the method of waveguide mode excitation

    Energy Technology Data Exchange (ETDEWEB)

    Sokolov, V I; Marusin, N V; Panchenko, V Ya; Savelyev, A G; Seminogov, V N; Khaydukov, E V [Institute on Laser and Information Technologies, Russian Academy of Sciences, Shatura, Moscow Region (Russian Federation)

    2013-12-31

    We propose a method for measuring simultaneously the refractive index n{sub f}, extinction coefficient m{sub f} and thickness H{sub f} of thin films. The method is based on the resonant excitation of waveguide modes in the film by a TE- or a TM-polarised laser beam in the geometry of frustrated total internal reflection. The values of n{sub f}, m{sub f} and H{sub f} are found by minimising the functional φ = [N{sup -1}Σ{sup N}{sub i=1}(R{sub exp}(θ{sub i}) – R{sub thr}(θ{sub i})){sup 2}]{sup 1/2}, where R{sub exp}(θ{sub i}) and R{sub thr}(θ{sub i}) are the experimental and theoretical coefficients of reflection of the light beam from the interface between the measuring prism and the film at an angle of incidence θ{sub i}. The errors in determining n{sub f}, m{sub f} and H{sub f} by this method are ±2 × 10{sup -4}, ±1 × 10{sup -3} and ±0.5%, respectively. (fiber and integrated optics)

  3. Apparent molar volumes and viscosity B-coefficients of caffeine in aqueous thorium nitrate solutions at T = (298.15, 308.15, and 318.15) K

    Energy Technology Data Exchange (ETDEWEB)

    Sinha, Biswajit, E-mail: biswachem@gmail.co [Department of Chemistry, University of North Bengal, Darjeeling 734013 (India); Roy, Pran Kumar; Sarkar, Bipul Kumar; Brahman, Dhiraj [Department of Chemistry, University of North Bengal, Darjeeling 734013 (India); Roy, Mahendra Nath, E-mail: mahendraroy2002@yahoo.co.i [Department of Chemistry, University of North Bengal, Darjeeling 734013 (India)

    2010-03-15

    Apparent molar volumes phi{sub V} and viscosity B-coefficients for caffeine in (0.00, 0.03, 0.05, and 0.07) mol . dm{sup -3} aqueous thorium nitrate, Th(NO{sub 3}){sub 4}, solutions were determined from solution density and viscosity measurements over the temperature range (298.15 to 318.15) K as function of concentration of caffeine and the relation: phi{sub V}{sup 0}=a{sub 0}+a{sub 1}T+a{sub 2}T{sup 2}, have been used to describe the temperature dependence of the standard partial molar volumes phi{sub V}{sup 0}. These results have been used to deduce the standard volumes of transfer DELTAphi{sub V}{sup 0} and viscosity B-coefficients of transfer DELTAB for caffeine from water to aqueous Th(NO{sub 3}){sub 4} solutions for rationalizing various interactions in the ternary solutions. The structure-making or breaking ability of caffeine has been discussed in terms of the sign of (delta{sup 2}phi{sub V}{sup 0}/deltaT{sup 2}){sub P}. The Friedman-Krishnan co-sphere model was used to explain the transfer volume of caffeine with increasing Th(NO{sub 3}){sub 4} molarity. The activation parameters of viscous flow for the ternary solutions were also discussed in terms of transition state theory.

  4. Apparent molar volumes and viscosity B-coefficients of caffeine in aqueous thorium nitrate solutions at T = (298.15, 308.15, and 318.15) K

    International Nuclear Information System (INIS)

    Sinha, Biswajit; Roy, Pran Kumar; Sarkar, Bipul Kumar; Brahman, Dhiraj; Roy, Mahendra Nath

    2010-01-01

    Apparent molar volumes φ V and viscosity B-coefficients for caffeine in (0.00, 0.03, 0.05, and 0.07) mol . dm -3 aqueous thorium nitrate, Th(NO 3 ) 4 , solutions were determined from solution density and viscosity measurements over the temperature range (298.15 to 318.15) K as function of concentration of caffeine and the relation: φ V 0 =a 0 +a 1 T+a 2 T 2 , have been used to describe the temperature dependence of the standard partial molar volumes φ V 0 . These results have been used to deduce the standard volumes of transfer Δφ V 0 and viscosity B-coefficients of transfer ΔB for caffeine from water to aqueous Th(NO 3 ) 4 solutions for rationalizing various interactions in the ternary solutions. The structure-making or breaking ability of caffeine has been discussed in terms of the sign of (δ 2 φ V 0 /δT 2 ) P . The Friedman-Krishnan co-sphere model was used to explain the transfer volume of caffeine with increasing Th(NO 3 ) 4 molarity. The activation parameters of viscous flow for the ternary solutions were also discussed in terms of transition state theory.

  5. Digital Cover Photography for Estimating Leaf Area Index (LAI in Apple Trees Using a Variable Light Extinction Coefficient

    Directory of Open Access Journals (Sweden)

    Carlos Poblete-Echeverría

    2015-01-01

    Full Text Available Leaf area index (LAI is one of the key biophysical variables required for crop modeling. Direct LAI measurements are time consuming and difficult to obtain for experimental and commercial fruit orchards. Devices used to estimate LAI have shown considerable errors when compared to ground-truth or destructive measurements, requiring tedious site-specific calibrations. The objective of this study was to test the performance of a modified digital cover photography method to estimate LAI in apple trees using conventional digital photography and instantaneous measurements of incident radiation (Io and transmitted radiation (I through the canopy. Leaf area of 40 single apple trees were measured destructively to obtain real leaf area index (LAID, which was compared with LAI estimated by the proposed digital photography method (LAIM. Results showed that the LAIM was able to estimate LAID with an error of 25% using a constant light extinction coefficient (k = 0.68. However, when k was estimated using an exponential function based on the fraction of foliage cover (ff derived from images, the error was reduced to 18%. Furthermore, when measurements of light intercepted by the canopy (Ic were used as a proxy value for k, the method presented an error of only 9%. These results have shown that by using a proxy k value, estimated by Ic, helped to increase accuracy of LAI estimates using digital cover images for apple trees with different canopy sizes and under field conditions.

  6. Digital cover photography for estimating leaf area index (LAI) in apple trees using a variable light extinction coefficient.

    Science.gov (United States)

    Poblete-Echeverría, Carlos; Fuentes, Sigfredo; Ortega-Farias, Samuel; Gonzalez-Talice, Jaime; Yuri, Jose Antonio

    2015-01-28

    Leaf area index (LAI) is one of the key biophysical variables required for crop modeling. Direct LAI measurements are time consuming and difficult to obtain for experimental and commercial fruit orchards. Devices used to estimate LAI have shown considerable errors when compared to ground-truth or destructive measurements, requiring tedious site-specific calibrations. The objective of this study was to test the performance of a modified digital cover photography method to estimate LAI in apple trees using conventional digital photography and instantaneous measurements of incident radiation (Io) and transmitted radiation (I) through the canopy. Leaf area of 40 single apple trees were measured destructively to obtain real leaf area index (LAI(D)), which was compared with LAI estimated by the proposed digital photography method (LAI(M)). Results showed that the LAI(M) was able to estimate LAI(D) with an error of 25% using a constant light extinction coefficient (k = 0.68). However, when k was estimated using an exponential function based on the fraction of foliage cover (f(f)) derived from images, the error was reduced to 18%. Furthermore, when measurements of light intercepted by the canopy (Ic) were used as a proxy value for k, the method presented an error of only 9%. These results have shown that by using a proxy k value, estimated by Ic, helped to increase accuracy of LAI estimates using digital cover images for apple trees with different canopy sizes and under field conditions.

  7. Digital Cover Photography for Estimating Leaf Area Index (LAI) in Apple Trees Using a Variable Light Extinction Coefficient

    Science.gov (United States)

    Poblete-Echeverría, Carlos; Fuentes, Sigfredo; Ortega-Farias, Samuel; Gonzalez-Talice, Jaime; Yuri, Jose Antonio

    2015-01-01

    Leaf area index (LAI) is one of the key biophysical variables required for crop modeling. Direct LAI measurements are time consuming and difficult to obtain for experimental and commercial fruit orchards. Devices used to estimate LAI have shown considerable errors when compared to ground-truth or destructive measurements, requiring tedious site-specific calibrations. The objective of this study was to test the performance of a modified digital cover photography method to estimate LAI in apple trees using conventional digital photography and instantaneous measurements of incident radiation (Io) and transmitted radiation (I) through the canopy. Leaf area of 40 single apple trees were measured destructively to obtain real leaf area index (LAID), which was compared with LAI estimated by the proposed digital photography method (LAIM). Results showed that the LAIM was able to estimate LAID with an error of 25% using a constant light extinction coefficient (k = 0.68). However, when k was estimated using an exponential function based on the fraction of foliage cover (ff) derived from images, the error was reduced to 18%. Furthermore, when measurements of light intercepted by the canopy (Ic) were used as a proxy value for k, the method presented an error of only 9%. These results have shown that by using a proxy k value, estimated by Ic, helped to increase accuracy of LAI estimates using digital cover images for apple trees with different canopy sizes and under field conditions. PMID:25635411

  8. The CPA Equation of State and an Activity Coefficient Model for Accurate Molar Enthalpy Calculations of Mixtures with Carbon Dioxide and Water/Brine

    Energy Technology Data Exchange (ETDEWEB)

    Myint, P. C. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Hao, Y. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Firoozabadi, A. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2015-03-27

    Thermodynamic property calculations of mixtures containing carbon dioxide (CO2) and water, including brines, are essential in theoretical models of many natural and industrial processes. The properties of greatest practical interest are density, solubility, and enthalpy. Many models for density and solubility calculations have been presented in the literature, but there exists only one study, by Spycher and Pruess, that has compared theoretical molar enthalpy predictions with experimental data [1]. In this report, we recommend two different models for enthalpy calculations: the CPA equation of state by Li and Firoozabadi [2], and the CO2 activity coefficient model by Duan and Sun [3]. We show that the CPA equation of state, which has been demonstrated to provide good agreement with density and solubility data, also accurately calculates molar enthalpies of pure CO2, pure water, and both CO2-rich and aqueous (H2O-rich) mixtures of the two species. It is applicable to a wider range of conditions than the Spycher and Pruess model. In aqueous sodium chloride (NaCl) mixtures, we show that Duan and Sun’s model yields accurate results for the partial molar enthalpy of CO2. It can be combined with another model for the brine enthalpy to calculate the molar enthalpy of H2O-CO2-NaCl mixtures. We conclude by explaining how the CPA equation of state may be modified to further improve agreement with experiments. This generalized CPA is the basis of our future work on this topic.

  9. Different trends in extreme and median surface aerosol extinction coefficients over China inferred from quality-controlled visibility data

    Science.gov (United States)

    Li, Jing; Li, Chengcai; Zhao, Chunsheng

    2018-03-01

    Although the temporal changes in aerosol properties have been widely investigated, the majority of studies has focused on average conditions without much emphasis on the extremes. However, the latter can be more important in terms of human health and climate change. This study uses a previously validated, quality-controlled visibility dataset to investigate the long-term trends (expressed in terms of relative changes) in extreme surface aerosol extinction coefficient (AEC) over China and compares them with the median trends. Two methods are used to independently evaluate the trends, which arrive at consistent results. The signs of extreme and median trends are generally coherent, whereas their magnitudes show distinct spatial and temporal differences. In the 1980s, an overall positive trend is found throughout China with the extreme trend exceeding the mean trend, except for northwest China and the North China Plain. In the 1990s, AEC over northeast and northwest China started to decline while the rest of the country still exhibited an increase. The extreme trends continued to dominate in the south while they yielded to the mean trend in the north. After the year 2000, the extreme trend became weaker than the mean trend overall in terms of both the magnitude and significance level. The annual trend can be primarily attributed to winter and fall trends. The results suggest that the decadal changes in pollution in China may be governed by different mechanisms. Synoptic conditions that often result in extreme air quality changes might have dominated in the 1980s, whereas emission increase might have been the main factor for the 2000s.

  10. Atmospheric Extinction Coefficients in the Ic Band for Several Major International Observatories: Results from the BiSON Telescopes, 1984-2016

    Science.gov (United States)

    Hale, S. J.; Chaplin, W. J.; Davies, G. R.; Elsworth, Y. P.; Howe, R.; Lund, M. N.; Moxon, E. Z.; Thomas, A.; Pallé, P. L.; Rhodes, E. J., Jr.

    2017-09-01

    Over 30 years of solar data have been acquired by the Birmingham Solar Oscillations Network (BiSON), an international network of telescopes used to study oscillations of the Sun. Five of the six BiSON telescopes are located at major observatories. The observational sites are, in order of increasing longitude: Mount Wilson (Hale) Observatory (MWO), California, USA; Las Campanas Observatory, Chile; Observatorio del Teide, Izaña, Tenerife, Canary Islands; the South African Astronomical Observatory, Sutherland, South Africa; Carnarvon, Western Australia; and the Paul Wild Observatory, Narrabri, New South Wales, Australia. The BiSON data may be used to measure atmospheric extinction coefficients in the {{{I}}}{{c}} band (approximately 700-900 nm), and presented here are the derived atmospheric extinction coefficients from each site over the years 1984-2016.

  11. SAMPL5: 3D-RISM partition coefficient calculations with partial molar volume corrections and solute conformational sampling.

    Science.gov (United States)

    Luchko, Tyler; Blinov, Nikolay; Limon, Garrett C; Joyce, Kevin P; Kovalenko, Andriy

    2016-11-01

    Implicit solvent methods for classical molecular modeling are frequently used to provide fast, physics-based hydration free energies of macromolecules. Less commonly considered is the transferability of these methods to other solvents. The Statistical Assessment of Modeling of Proteins and Ligands 5 (SAMPL5) distribution coefficient dataset and the accompanying explicit solvent partition coefficient reference calculations provide a direct test of solvent model transferability. Here we use the 3D reference interaction site model (3D-RISM) statistical-mechanical solvation theory, with a well tested water model and a new united atom cyclohexane model, to calculate partition coefficients for the SAMPL5 dataset. The cyclohexane model performed well in training and testing ([Formula: see text] for amino acid neutral side chain analogues) but only if a parameterized solvation free energy correction was used. In contrast, the same protocol, using single solute conformations, performed poorly on the SAMPL5 dataset, obtaining [Formula: see text] compared to the reference partition coefficients, likely due to the much larger solute sizes. Including solute conformational sampling through molecular dynamics coupled with 3D-RISM (MD/3D-RISM) improved agreement with the reference calculation to [Formula: see text]. Since our initial calculations only considered partition coefficients and not distribution coefficients, solute sampling provided little benefit comparing against experiment, where ionized and tautomer states are more important. Applying a simple [Formula: see text] correction improved agreement with experiment from [Formula: see text] to [Formula: see text], despite a small number of outliers. Better agreement is possible by accounting for tautomers and improving the ionization correction.

  12. SAMPL5: 3D-RISM partition coefficient calculations with partial molar volume corrections and solute conformational sampling

    Science.gov (United States)

    Luchko, Tyler; Blinov, Nikolay; Limon, Garrett C.; Joyce, Kevin P.; Kovalenko, Andriy

    2016-11-01

    Implicit solvent methods for classical molecular modeling are frequently used to provide fast, physics-based hydration free energies of macromolecules. Less commonly considered is the transferability of these methods to other solvents. The Statistical Assessment of Modeling of Proteins and Ligands 5 (SAMPL5) distribution coefficient dataset and the accompanying explicit solvent partition coefficient reference calculations provide a direct test of solvent model transferability. Here we use the 3D reference interaction site model (3D-RISM) statistical-mechanical solvation theory, with a well tested water model and a new united atom cyclohexane model, to calculate partition coefficients for the SAMPL5 dataset. The cyclohexane model performed well in training and testing (R=0.98 for amino acid neutral side chain analogues) but only if a parameterized solvation free energy correction was used. In contrast, the same protocol, using single solute conformations, performed poorly on the SAMPL5 dataset, obtaining R=0.73 compared to the reference partition coefficients, likely due to the much larger solute sizes. Including solute conformational sampling through molecular dynamics coupled with 3D-RISM (MD/3D-RISM) improved agreement with the reference calculation to R=0.93. Since our initial calculations only considered partition coefficients and not distribution coefficients, solute sampling provided little benefit comparing against experiment, where ionized and tautomer states are more important. Applying a simple pK_{ {a}} correction improved agreement with experiment from R=0.54 to R=0.66, despite a small number of outliers. Better agreement is possible by accounting for tautomers and improving the ionization correction.

  13. Seasonal atmospheric extinction

    International Nuclear Information System (INIS)

    Mikhail, J.S.

    1979-01-01

    Mean monochromatic extinction coefficients at various wavelengths at the Kottamia Observatory site have shown the existence of a seasonal variation of atmospheric extinction. The extinction of aerosol compontnts with wavelengths at winter represent exceedingly good conditions. Spring gives the highest extinction due to aerosol. (orig.)

  14. On-site ocean horizontal aerosol extinction coefficient inversion under different weather conditions on the Bo-hai and Huang-hai Seas

    Science.gov (United States)

    Zeng, Xianjiang; Xia, Min; Ge, Yinghui; Guo, Wenping; Yang, Kecheng

    2018-03-01

    In this paper, we explore the horizontal extinction characteristics under different weather conditions on the ocean surface with on-site experiments on the Bo-hai and Huang-hai Seas in the summer of 2016. An experimental lidar system is designed to collect the on-site experimental data. By aiming at the inhomogeneity and uncertainty of the horizontal aerosol in practice, a joint retrieval method is proposed to retrieve the aerosol extinction coefficients (AEC) from the raw data along the optical path. The retrieval results of both the simulated and the real signals demonstrate that the joint retrieval method is practical. Finally, the sequence observation results of the on-site experiments under different weather conditions are reported and analyzed. These results can provide the attenuation information to analyze the atmospheric aerosol characteristics on the ocean surface.

  15. Molar Pregnancy

    Science.gov (United States)

    ... weeks of pregnancy Ovarian cysts Anemia Overactive thyroid (hyperthyroidism) Causes A molar pregnancy is caused by an ... have this complication than a partial molar pregnancy. Prevention If you've had a molar pregnancy, talk ...

  16. Molar mass, radius of gyration and second virial coefficient from new static light scattering equations for dilute solutions: application to 21 (macro)molecules.

    Science.gov (United States)

    Illien, Bertrand; Ying, Ruifeng

    2009-05-11

    New static light scattering (SLS) equations for dilute binary solutions are derived. Contrarily to the usual SLS equations [Carr-Zimm (CZ)], the new equations have no need for the experimental absolute Rayleigh ratio of a reference liquid and solely rely on the ratio of scattered intensities of solutions and solvent. The new equations, which are based on polarizability equations, take into account the usual refractive index increment partial differential n/partial differential rho(2) complemented by the solvent specific polarizability and a term proportional to the slope of the solution density rho versus the solute mass concentration rho(2) (density increment). Then all the equations are applied to 21 (macro)molecules with a wide range of molar mass (0.2equations clearly achieve a better agreement with supplier M values. For macromolecules (M>500 kg mol(-1)), for which the scattered intensity is no longer independent of the scattering angle, the new equations give the same value of the radius of gyration as the CZ equation and consistent values of the second virial coefficient.

  17. MOLAR UPRIGHTING

    Directory of Open Access Journals (Sweden)

    Eka Erwansyah

    2006-04-01

    Full Text Available The mesial tipping of molar is frequently found in orthodontic cases. This molar malposition must be corrected since it may cause periodontal disorders, occlusal interferences, and temporomandibular joint dysfunction, and is often needed in planning a fixed bridge. This paper is a literature study to discuss about appliance designs, indication, and contraindications, and complication and treatment protocols of molar uprighting by fixed orthodontic appliances. By knowing the techniques of molar uprighting, the moments mentioned above can be avoided.

  18. A comparison study for mass attenuation coefficients of some amino acids using MCNP code

    Energy Technology Data Exchange (ETDEWEB)

    Vahabi, Seyed Milad; Bahreynipour, Mostean; Shamsaie-Zafarghandi, Mojtaba [Amirkabir Univ. of Technology, Tehran (Iran, Islamic Republic of). Dept. of Energy Engineering and Physics

    2017-07-15

    In this study, a novel model of MCNP4C code reported recently was used to determine the photon mass attenuation coefficients of some amino acids at energies, 123, 360, 511, 662, 1170, 1280 and 1330 keV. The simulation results were compared with the XCOM data. It was indicated that the results were highly close to the calculated XCOM values. Obtained results were used to calculate the molar extinction coefficient. All the results showed the convenience and usefulness of the model in calculation of mass attenuation coefficients of amino acids.

  19. Rethinking Extinction

    Science.gov (United States)

    Dunsmoor, Joseph E.; Niv, Yael; Daw, Nathaniel; Phelps, Elizabeth A.

    2015-01-01

    Extinction serves as the leading theoretical framework and experimental model to describe how learned behaviors diminish through absence of anticipated reinforcement. In the past decade, extinction has moved beyond the realm of associative learning theory and behavioral experimentation in animals and has become a topic of considerable interest in the neuroscience of learning, memory, and emotion. Here, we review research and theories of extinction, both as a learning process and as a behavioral technique, and consider whether traditional understandings warrant a re-examination. We discuss the neurobiology, cognitive factors, and major computational theories, and revisit the predominant view that extinction results in new learning that interferes with expression of the original memory. Additionally, we reconsider the limitations of extinction as a technique to prevent the relapse of maladaptive behavior, and discuss novel approaches, informed by contemporary theoretical advances, that augment traditional extinction methods to target and potentially alter maladaptive memories. PMID:26447572

  20. Rethinking Extinction

    OpenAIRE

    Dunsmoor, Joseph E.; Niv, Yael; Daw, Nathaniel; Phelps, Elizabeth A.

    2015-01-01

    Extinction serves as the leading theoretical framework and experimental model to describe how learned behaviors diminish through absence of anticipated reinforcement. In the past decade, extinction has moved beyond the realm of associative learning theory and behavioral experimentation in animals and has become a topic of considerable interest in the neuroscience of learning, memory, and emotion. Here, we review research and theories of extinction, both as a learning process and as a behavior...

  1. Deciduous molar hypomineralization and molar incisor hypomineralization

    NARCIS (Netherlands)

    Elfrink, M.E.C.; ten Cate, J.M.; Jaddoe, V.W.V.; Hofman, A.; Moll, H.A.; Veerkamp, J.S.J.

    2012-01-01

    This study was embedded in the Generation R Study, a population-based prospective cohort study from fetal life until young adulthood. This study focused on the relationship between Deciduous Molar Hypomineralization (DMH) and Molar Incisor Hypomineralization (MIH). First permanent molars develop

  2. THE SECONDARY EXTINCTION CORRECTION

    Energy Technology Data Exchange (ETDEWEB)

    Zachariasen, W. H.

    1963-03-15

    It is shown that Darwin's formula for the secondary extinction correction, which has been universally accepted and extensively used, contains an appreciable error in the x-ray diffraction case. The correct formula is derived. As a first order correction for secondary extinction, Darwin showed that one should use an effective absorption coefficient mu + gQ where an unpolarized incident beam is presumed. The new derivation shows that the effective absorption coefficient is mu + 2gQ(1 + cos/sup 4/2 theta )/(1 plus or minus cos/sup 2/2 theta )/s up 2/, which gives mu + gQ at theta =0 deg and theta = 90 deg , but mu + 2gQ at theta = 45 deg . Darwin's theory remains valid when applied to neutron diffraction. (auth)

  3. [Correlation between the lower first permanent molar axis and the premature loss of temporary molars].

    Science.gov (United States)

    Petcu, Ana; Maxim, A; Haba, Danisia

    2009-01-01

    The aim of our study was to determine the impact of premature loss of temporary molars upon the longitudinal axis of the first permanent molar. The study sample was formed by 94 orthopanthomografies of child patients with premature loss of lower temporary molars (first or second) after clinical eruption of the first permanent molar. All panoramic radiographs have been realized with the same panoramic unit with 1.4% magnification coefficient and were analyzed using a standardized technique of tracing the images of teeth and bone on matte acetate paper. It was evaluated the angle between longitudinal axis of first permanent lower molar and occlusal plane. It was observed that premature loss of lower second deciduous molar modifies greater the vertical axis of first permanent molar (between 61 degrees and 79 degrees) then premature loss of first lower primary molar. This is perhaps because the loss of space in the case of premature exfoliation of first primary molar is due more to distal drift of canine then mesial drift of molars. The drift to mesial of first permanent molar is more accentuated proportional with the age at which appeared premature loss and so it is loss of leeway space.

  4. ASOS Surface Extinction Coefficient by STI

    Data.gov (United States)

    Washington University St Louis — ASOS_STI represents a 250-station subset of the national ASOS SURF_MET dataset. The unique feature of this data is that the visibility sensor values are available in...

  5. 二氧化碳与2-丁醇二元体系在高压下的亨利系数和偏摩尔体积性质计算%Calculation of Henry's coefficient and partial molar volume of carbon dioxide in 2-butanol at elevated pressures

    Institute of Scientific and Technical Information of China (English)

    田爱琴; 孙洪博; 陈文涛; 王琳

    2012-01-01

    Based on vapor-liquid phase equilibria data for CO2+2-butanol binary system from 323K to 353K by constant-volume visual high-pressure cell, the solubility model of CO2 in 2-butanol was established with Krichevsky-Kasarnovsky equation. Henry's coefficients and partial molar volumes of CO2 at infinite dilution were calculated. Meanwhile, Partial molar volumes of CO2 and 2-butanol at equilibrium were calculated from partial molar volumes properties together with Peng-Robinson equation of state and Van der Waals-2 mixed rule. The results showed that Henry's coefficients and partial molar volumes of CO2 at infinite dilution were both the function of temperature, and Henry's coefficients decreased with temperature. The partial molar volumes of CO2 at infinite dilution were negative and the magnitudes decreased with temperature. The calculated effects of partial molar volumes of vapor and liquid phase at equilibrium showed that the partial molar volumes of CO2 and 2-butanol in liquid phase were positive, but in vapor the partial molar volumes of CO2 were negative and the partial molar volumes of 2-butanol were positive. The research provided theoretical basis for deciding supercritical extraction conditions and instructing industrial production.%利用固定体积可视高压釜测量出的在323 K~353 K温度范围内的CO2与2-丁醇二元体系在高压下的汽液相平衡数据,根据Krichevsky-Kasarnovsky方程建立了CO2在液相中的溶解度模型,得到了该二元体系在高压下的亨利系数和CO2在无限稀释溶液中的偏摩尔体积等性质.同时根据偏摩尔体积性质和Peng-Robinson状态方程及Van der Waals-2混合规则来计算该体系在平衡状态下的气、液相的偏摩尔体积.结果表明CO2在2-丁醇中的亨利系数和CO2在无限稀释溶液中的偏摩尔体积均为温度的函数,CO2在2-丁醇中的亨利系数随温度的升高而降低.CO2在无限稀释溶液中的偏摩尔体积(V)1∞在研究温度下均为

  6. [Hyperthyroidism in molar pregnancy].

    Science.gov (United States)

    Boufettal, H; Mahdoui, S; Noun, M; Hermas, S; Samouh, N

    2014-03-01

    Hyperthyroidism is a rare complication of molar pregnancy. We report a 39-year-old woman who presented a thyrotoxic syndrome accompanying a molar pregnancy. Serum thyroid hormones were elevated and returned to normal level after uterine evacuation of a molar pregnancy. The authors detail the role of thyroid stimulating property of human gonadotropin chorionic hormone and its structural changes during the gestational trophoblastic diseases. These changes give the latter the thyroid stimulating properties and signs of hyperthyroidism. Molar pregnancy may be a cause of hyperthyroidism. The diagnosis of molar pregnancy should be a mention to thyrotoxicosique syndrome in a woman of childbearing age. Copyright © 2013. Published by Elsevier SAS.

  7. Interstellar Extinction

    OpenAIRE

    Gontcharov, George

    2017-01-01

    This review describes our current understanding of interstellar extinction. This differ substantially from the ideas of the 20th century. With infrared surveys of hundreds of millions of stars over the entire sky, such as 2MASS, SPITZER-IRAC, and WISE, we have looked at the densest and most rarefied regions of the interstellar medium at distances of a few kpc from the sun. Observations at infrared and microwave wavelengths, where the bulk of the interstellar dust absorbs and radiates, have br...

  8. Lidar extinction measurement in the mid infrared

    Science.gov (United States)

    Mitev, Valentin; Babichenko, S.; Borelli, R.; Fiorani, L.; Grigorov, I.; Nuvoli, M.; Palucci, A.; Pistilli, M.; Puiu, Ad.; Rebane, Ott; Santoro, S.

    2014-11-01

    We present a lidar measurement of atmospheric extinction coefficient. The measurement is performed by inversion of the backscatter lidar signal at wavelengths 3'000nm and 3'500nm. The inversion of the backscatter lidar signal was performed with constant extinction-to-backscatter ration values of 104 and exponential factor 0.1.

  9. The atmospheric extinction of light

    International Nuclear Information System (INIS)

    Hughes, Stephen W; Powell, Sean; Carroll, Joshua; Cowley, Michael

    2016-01-01

    An experiment is described that enables students to understand the properties of atmospheric extinction due to Rayleigh scattering. The experiment requires the use of red, green and blue lasers attached to a travelling microscope or similar device. The laser beams are passed through an artificial atmosphere, made from milky water, at varying depths, before impinging on either a light meter or a photodiode integral to a Picotech Dr. DAQ ADC. A plot of measured spectral intensity verses depth reveals the contribution Rayleigh scattering has to the extinction coefficient. For the experiment with the light meter, the extinction coefficients for red, green and blue light in the milky sample of water were 0.27, 0.36 and 0.47 cm −1 respectively and 0.032, 0.037 and 0.092 cm −1 for the Picotech Dr. DAQ ADC. (paper)

  10. Removable molar power arm

    Directory of Open Access Journals (Sweden)

    Raj Kumar Verma

    2013-01-01

    Full Text Available Attachment of force elements from the gingival hook of maxillary molar tubes during the retraction of the anterior teeth is very common in orthodontic practice. As the line of force passes below the center of resistance (CR of molar, it results its mesial tipping and also anchorage loss. To overcome this problem, the line of force should pass along the CR of molar. This article highlights a method to overcome this problem by attaching a removable power arm to the headgear tube of molar tube during the retraction of the anterior teeth.

  11. Impossible Extinction

    Science.gov (United States)

    Cockell, Charles S.

    2003-03-01

    Every 225 million years the Earth, and all the life on it, completes one revolution around the Milky Way Galaxy. During this remarkable journey, life is influenced by calamitous changes. Comets and asteroids strike the surface of the Earth, stars explode, enormous volcanoes erupt, and, more recently, humans litter the planet with waste. Many animals and plants become extinct during the voyage, but humble microbes, simple creatures made of a single cell, survive this journey. This book takes a tour of the microbial world, from the coldest and deepest places on Earth to the hottest and highest, and witnesses some of the most catastrophic events that life can face. Impossible Extinction tells this remarkable story to the general reader by explaining how microbes have survived on Earth for over three billion years. Charles Cockell received his doctorate from the University of Oxford, and is currently a microbiologist with rhe Search for Extraterrestrial Intelligence Institute (SETI), based at the British Antarctic Survey in Cambridge, UK. His research focusses on astrobiology, life in the extremes and the human exploration of Mars. Cockell has been on expeditions to the Arctic, Antarctic, Mongolia, and in 1993 he piloted a modified insect-collecting ultra-light aircraft over the Indonesian rainforests. He is Chair of the Twenty-one Eleven Foundation for Exploration, a charity that supports expeditions that forge links between space exploration and environmentalism.

  12. Association of the Mandibular Third Molar Position to the Pericoronitis

    Directory of Open Access Journals (Sweden)

    Tsvetan Tsvetanov

    2018-02-01

    Full Text Available Introduction: Pericoronitis is inflammation of the soft tissues surrounding the crown of a partially erupted tooth. Objective: To provide measurement of lower third molar angulation and determine relationship between mandibular third molar position and presence of pericoronitis. Material and methods: We studied 104 patients with lower third molar pericoronitis with clinical manifestations and measurement of lower third molar angulation. The mean age of patients was 25.7 years (range 18-35 years. Results: In this study was used the following statistical analysis, Pearson correlation coefficient and Spearman’s correlation coefficient (nonparametric version of the Pearson correlation coefficient for measure of the linear correlation between two variables - pericoronitis and angulation of the lower third molars. The chi-square test was used to assesses case incidences. The level of significance was p<0.05. 36.04% of partially impacted mandibular third molars were mesioangular followed by the vertical (25.47%, horizontal (18.97%, distoangular (9.21%, buccal (5.42% and lingual (3.79% position. The lowest part of the mandibular third molars is located in the ramus of mandible (1.08%. The present study was found in relation to mesioangular, distoangular, vertical impaction and pericoronitis (p<0.05. Conclusion: We conclude that the position of lower third molar may be able to be associated with presence of pericoronitis.

  13. Third molar development: measurements versus scores as age predictor.

    Science.gov (United States)

    Thevissen, P W; Fieuws, S; Willems, G

    2011-10-01

    Human third molar development is widely used to predict chronological age of sub adult individuals with unknown or doubted age. For these predictions, classically, the radiologically observed third molar growth and maturation is registered using a staging and related scoring technique. Measures of lengths and widths of the developing wisdom tooth and its adjacent second molar can be considered as an alternative registration. The aim of this study was to verify relations between mandibular third molar developmental stages or measurements of mandibular second molar and third molars and age. Age related performance of stages and measurements were compared to assess if measurements added information to age predictions from third molar formation stage. The sample was 340 orthopantomograms (170 females, 170 males) of individuals homogenously distributed in age between 7 and 24 years. Mandibular lower right, third and second molars, were staged following Gleiser and Hunt, length and width measurements were registered, and various ratios of these measurements were calculated. Univariable regression models with age as response and third molar stage, measurements and ratios of second and third molars as predictors, were considered. Multivariable regression models assessed if measurements or ratios added information to age prediction from third molar stage. Coefficients of determination (R(2)) and root mean squared errors (RMSE) obtained from all regression models were compared. The univariable regression model using stages as predictor yielded most accurate age predictions (males: R(2) 0.85, RMSE between 0.85 and 1.22 year; females: R(2) 0.77, RMSE between 1.19 and 2.11 year) compared to all models including measurements and ratios. The multivariable regression models indicated that measurements and ratios added no clinical relevant information to the age prediction from third molar stage. Ratios and measurements of second and third molars are less accurate age predictors

  14. Human dental age estimation combining third molar(s) development and tooth morphological age predictors.

    Science.gov (United States)

    Thevissen, P W; Galiti, D; Willems, G

    2012-11-01

    In the subadult age group, third molar development, as well as age-related morphological tooth information can be observed on panoramic radiographs. The aim of present study was to combine, in subadults, panoramic radiographic data based on developmental stages of third molar(s) and morphological measurements from permanent teeth, in order to evaluate its added age-predicting performances. In the age range between 15 and 23 years, 25 gender-specific radiographs were collected within each age category of 1 year. Third molar development was classified and registered according the 10-point staging and scoring technique proposed by Gleiser and Hunt (1955), modified by Köhler (1994). The Kvaal (1995) measuring technique was applied on the indicated teeth from the individuals' left side. Linear regression models with age as response and third molar-scored stages as explanatory variables were developed, and morphological measurements from permanent teeth were added. From the models, determination coefficients (R (2)) and root-mean-square errors (RMSE) were calculated. Maximal-added age information was reported as a 6 % R² increase and a 0.10-year decrease of RMSE. Forensic dental age estimations on panoramic radiographic data in the subadult group (15-23 year) should only be based on third molar development.

  15. Ruptured tubal molar pregnancy

    African Journals Online (AJOL)

    2011-05-19

    May 19, 2011 ... In most instances, moles develop within the uterine cavity, but may occur at ... Patients with tubal molar pregnancy are very difficult to distinguish .... There was a left-sided adnexal mass, whose size could not be appreciated ...

  16. Molar Incisor Hypomineralisation

    NARCIS (Netherlands)

    Elfrink, M.; Weerheijm, K.L.

    2013-01-01

    Molar Incisor Hypomineralisation (mih) wordt omschreven als een hypomineralisatie (van systemische oorsprong) van één tot vier blijvende eerste molaren, vaak in combinatie met aangedane incisieven. mih-molaren zijn fragieler en cariësgevoeliger dan gewone molaren. Een kenmerk van mih-molaren is een

  17. Molar Incisor Hypomineralisation

    NARCIS (Netherlands)

    Elfrink, M.; Weerheijm, K.L.

    2009-01-01

    Molar Incisor Hypomineralisation (MIH) wordt gedefinieerd als een hypomineralisatie van systemische oorsprong van één tot vier blijvende eerste molaren, vaak in combinatie met aangedane incisieven. MIH-molaren zijn fragieler en cariësgevoeliger dan gewone molaren. Een kenmerk van MIH-molaren is een

  18. Molar Incisor Hypomineralisation

    NARCIS (Netherlands)

    Elfrink, M.; Weerheijm, K.

    2011-01-01

    Molar Incisor Hypomineralisation (mih ) wordt gedefinieerd als een hypomineralisatie van systemische oorsprong van één tot vier blijvende eerste molaren, vaak in combinatie met aangedane incisieven. mih -molaren zijn fragieler en cariësgevoeliger dan gewone molaren. Een kenmerk van mih -molaren is

  19. Modeling galactic extinction

    OpenAIRE

    Cecchi-Pestellini, C.; Mulas, G.; Casu, S.; Iatì, M. A.; Saija, R.; Cacciola, A.; Borghese, F.; Denti, P.

    2011-01-01

    We present a model for interstellar extinction dust, in which we assume a bimodal distribution of extinction carriers, a dispersion of core-mantle grains, supplemented by a collection of PAHs in free molecular form. We use state-of-the-art methods to calculate the extinction due to macroscopic dust particles, and the absorption cross-sections of PAHs in four different charge states. While successfull for most of observed Galactic extinction curves, in few cases the model cannot provide reliab...

  20. Modern examples of extinctions

    DEFF Research Database (Denmark)

    Lövei, Gabor L

    2013-01-01

    No species lives forever, and extinction is the ultimate fate of all living species. The fossil record indicates that a recent extinction wave affecting terrestrial vertebrates was parallel with the arrival of modern humans to areas formerly uninhabited by them. These modern instances of extinction...

  1. Bimodal extinction without cross-modal extinction.

    OpenAIRE

    Inhoff, A W; Rafal, R D; Posner, M J

    1992-01-01

    Three patients with unilateral neurological injury were clinically examined. All showed consistent unilateral extinction in the tactile and visual modalities on simultaneous intramodal stimulation. There was virtually no evidence for cross-modal extinction, however, so that contralateral stimulation of one modality would have extinguished perception of ipsilateral stimuli in the other modality. It is concluded that the attentional system controlling the encoding of tactile and visual stimuli ...

  2. Precision Photometric Extinction Corrections from Direct Atmospheric Measurements

    Science.gov (United States)

    McGraw, John T.; Zimmer, P.; Linford, J.; Simon, T.; Measurement Astrophysics Research Group

    2009-01-01

    For decades astronomical extinction corrections have been accomplished using nightly mean extinction coefficients derived from Langley plots measured with the same telescope used for photometry. Because this technique results in lost time on program fields, observers only grudgingly made sporadic extinction measurements. Occasionally extinction corrections are not measured nightly but are made using tabulated mean monthly or even quarterly extinction coefficients. Any observer of the sky knows that Earth's atmosphere is an ever-changing fluid in which is embedded extinction sources ranging from Rayleigh (molecular) scattering to aerosol, smoke and dust scattering and absorption, to "just plain cloudy.” Our eyes also tell us that the type, direction and degree of extinction changes on time scales of minutes or less - typically shorter than many astronomical observations. Thus, we should expect that atmospheric extinction can change significantly during a single observation. Mean extinction coefficients might be well-defined nightly means, but those means have high variance because they do not accurately record the wavelength-, time-, and angle-dependent extinction actually affecting each observation. Our research group is implementing lidar measurements made in the direction of observation with one minute cadence, from which the absolute monochromatic extinction can be measured. Simultaneous spectrophotometry of nearby bright standard stars allows derivation and MODTRAN modeling atmospheric transmission as a function of wavelength for the atmosphere through which an observation is made. Application of this technique is demonstrated. Accurate real-time extinction measurements are an enabling factor for sub-1% photometry. This research is supported by NSF Grant 0421087 and AFRL Grant #FA9451-04-2-0355.

  3. Extinction with multiple excitors

    OpenAIRE

    McConnell, Bridget L.; Miguez, Gonzalo; Miller, Ralph R.

    2013-01-01

    Four conditioned suppression experiments with rats, using an ABC renewal design, investigated the effects of compounding the target conditioned excitor with additional, nontarget conditioned excitors during extinction. Experiment 1 showed stronger extinction, as evidenced by less renewal, when the target excitor was extinguished in compound with a second excitor, relative to when it was extinguished with associatively neutral stimuli. Critically, this deepened extinction effect was attenuated...

  4. On the trap of extinction and its elimination

    International Nuclear Information System (INIS)

    Vitanov, Nikolay K.; Dimitrova, Zlatinka I.; Kantz, Holger

    2006-01-01

    We investigate the dynamics of a system of three interacting populations in presence of extinction and substitution: each population whose number of individuals drops under some threshold value becomes extinct, and it is substituted by another population with different fitness and different coefficients of interaction with the other populations. We study the influence of extinction on the system states, which in the absence of extinction can be fixed points, limit cycles or chaotic attractors of Shilnikov kind. The extinction can destabilize each of these states. We observe two possible kinds of evolution in the destabilized system: (i) it can remain forever in the trap of extinction, i.e., the extinctions and substitutions of populations continue for indefinitely long time or (ii) it can avoid the trap of extinction by means of the substitution, i.e., the fitness and the coefficients of the interactions between the species move the system attractor away from the zone of the threshold values, the extinction stops, and the system settles on a new attractor. The obtained results are discussed from the point of view of products competing for the preference of buyers that can change their opinion

  5. End Ordovician extinctions

    DEFF Research Database (Denmark)

    Harper, David A. T.; Hammarlund, Emma; Rasmussen, Christian M. Ø.

    2014-01-01

    -global anoxia associated with a marked transgression during the Late Hirnantian. Most recently, however, new drivers for the extinctions have been proposed, including widespread euxinia together with habitat destruction caused by plate tectonic movements, suggesting that the end Ordovician mass extinctions were...

  6. Excess molar volumes and partial molar volumes for (propionitrile + an alkanol) at T = 298.15 K and p = 0.1 MPa

    International Nuclear Information System (INIS)

    Deenadayalu, N.; Bhujrajh, P.

    2006-01-01

    The excess molar volumes and the partial molar volumes for (propionitrile + an alkanol) at T = 298.15 K and at atmospheric pressure are reported. The hydrogen bonding between the OH133;NC groups are discussed in terms of the chain length of the alkanol. The alkanols studied are (methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, and 1-pentanol). The excess molar volume data was fitted to the Redlich-Kister equation The partial molar volumes were calculated from the Redlich-Kister coefficients

  7. Extinction of NGC 7027

    International Nuclear Information System (INIS)

    Seaton, M.J.

    1979-01-01

    Emission intensities of recombination lines in hydrogenic spectra are known accurately relative to intensities in the free-free radio continuum. For NGC 7027 intensities have been measured for the radio continuum and for H I and He II lines in the wavelength range from lambda = 2.17 μm to lambda = 1640 A: comparison with the calculated emission intensities gives the extinction. Determinations of the standard interstellar extinction function are critically discussed. The extinction deduced for the total radiation from NGC 7027 has a dependence on wavelength for 6563 A >= lambda >= 1640 A which is in excellent agreement with the adopted standard results, but there are some anomalies for longer wavelengths and for the ratio of total to selective extinction. These can be explained using a model which allows for a local contribution to the extinction which is variable over the surface of the nebula. (author)

  8. Interstellar extinction correlations

    International Nuclear Information System (INIS)

    Jones, A.P.; Williams, D.A.; Duley, W.W.

    1987-01-01

    A recently proposed model for interstellar grains in which the extinction arises from small silicate cores with mantles of hydrogenated amorphous carbon (HAC or α-C:H), and large, but thinly coated, silicate grains can successfully explain many of the observed properties of interstellar dust. The small silicate cores give rise to the 2200 A extinction feature. The extinction in the visual is produced by the large silicates and the HAC mantles on the small cores, whilst the far UV extinction arises in the HAC mantles with a small contribution form the silicate grains. The grain model requires that the silicate material is the more resilient component and that variations in the observed extinction from region to region are due to the nature and depletion of the carbon in the HAC mantles. (author)

  9. Extinction and the fossil record

    Science.gov (United States)

    Sepkoski, J. J. Jr; Sepkoski JJ, ,. J. r. (Principal Investigator)

    1994-01-01

    The author examines evidence of mass extinctions in the fossil record and searches for reasons for such large extinctions. Five major mass extinctions eliminated at least 40 percent of animal genera in the oceans and from 65 to 95 percent of ocean species. Questions include the occurrence of gradual or catastrophic extinctions, causes, environment, the capacity of a perturbation to cause extinctions each time it happens, and the possibility and identification of complex events leading to a mass extinction.

  10. Is IR going extinct?

    Science.gov (United States)

    Mitchell, Audra

    2016-01-01

    A global extinction crisis may threaten the survival of most existing life forms. Influential discourses of ‘existential risk’ suggest that human extinction is a real possibility, while several decades of evidence from conservation biology suggests that the Earth may be entering a ‘sixth mass extinction event’. These conditions threaten the possibilities of survival and security that are central to most branches of International Relations. However, this discipline lacks a framework for addressing (mass) extinction. From notions of ‘nuclear winter’ and ‘omnicide’ to contemporary discourses on catastrophe, International Relations thinking has treated extinction as a superlative of death. This is a profound category mistake: extinction needs to be understood not in the ontic terms of life and death, but rather in the ontological context of be(com)ing and negation. Drawing on the work of theorists of the ‘inhuman’ such as Quentin Meillassoux, Claire Colebrook, Ray Brassier, Jean-Francois Lyotard and Nigel Clark, this article provides a pathway for thinking beyond existing horizons of survival and imagines a profound transformation of International Relations. Specifically, it outlines a mode of cosmopolitics that responds to the element of the inhuman and the forces of extinction. Rather than capitulating to narratives of tragedy, this cosmopolitics would make it possible to think beyond the restrictions of existing norms of ‘humanity’ to embrace an ethics of gratitude and to welcome the possibility of new worlds, even in the face of finitude.

  11. Temporal Dynamics of Recovery from Extinction Shortly after Extinction Acquisition

    Science.gov (United States)

    Archbold, Georgina E.; Dobbek, Nick; Nader, Karim

    2013-01-01

    Evidence suggests that extinction is new learning. Memory acquisition involves both short-term memory (STM) and long-term memory (LTM) components; however, few studies have examined early phases of extinction retention. Retention of auditory fear extinction was examined at various time points. Shortly (1-4 h) after extinction acquisition…

  12. Molar Incisiv Hypomineralisasjon - MIH Litteraturstudie

    OpenAIRE

    Khan, Aisha Farnaz

    2017-01-01

    Introduksjon: MIH er definert som emaljehypomineralisering av systemisk opprinnelse der 1 til 4 av første permanente molarer er rammet. Incisiver er også ofte affiserte. Hensikten med denne litteraturstudien er å lage en oversikt over, og vurdere tilgjengelig litteratur om MIH, og bruke litteraturen som bakgrunn for å utarbeide en informasjonsbrosjyre om MIH. Materiale og metode: Det ble utført et elektronisk søk i PubMed med søkestrengene ”Molar incisor hypomineralization MIH” og ”Molar inci...

  13. Mass extinction efficiency and extinction hygroscopicity of ambient PM2.5 in urban China.

    Science.gov (United States)

    Cheng, Zhen; Ma, Xin; He, Yujie; Jiang, Jingkun; Wang, Xiaoliang; Wang, Yungang; Sheng, Li; Hu, Jiangkai; Yan, Naiqiang

    2017-07-01

    The ambient PM 2.5 pollution problem in China has drawn substantial international attentions. The mass extinction efficiency (MEE) and hygroscopicity factor (f(RH)) of PM 2.5 can be readily applied to study the impacts on atmospheric visibility and climate. The few previous investigations in China only reported results from pilot studies and are lack of spatial representativeness. In this study, hourly average ambient PM 2.5 mass concentration, relative humidity, and atmospheric visibility data from China national air quality and meteorological monitoring networks were retrieved and analyzed. It includes 24 major Chinese cities from nine city-clusters with the period of October 2013 to September 2014. Annual average extinction coefficient in urban China was 759.3±258.3Mm -1 , mainly caused by dry PM 2.5 (305.8.2±131.0Mm -1 ) and its hygroscopicity (414.6±188.1Mm -1 ). High extinction coefficient values were resulted from both high ambient PM 2.5 concentration (68.5±21.7µg/m 3 ) and high relative humidity (69.7±8.6%). The PM 2.5 mass extinction efficiency varied from 2.87 to 6.64m 2 /g with an average of 4.40±0.84m 2 /g. The average extinction hygroscopic factor f(RH=80%) was 2.63±0.45. The levels of PM 2.5 mass extinction efficiency and hygroscopic factor in China were in comparable range with those found in developed countries in spite of the significant diversities among all 24 cities. Our findings help to establish quantitative relationship between ambient extinction coefficient (visual range) and PM 2.5 & relative humidity. It will reduce the uncertainty of extinction coefficient estimation of ambient PM 2.5 in urban China which is essential for the research of haze pollution and climate radiative forcing. Copyright © 2017 Elsevier Inc. All rights reserved.

  14. Stress and Fear Extinction

    Science.gov (United States)

    Maren, Stephen; Holmes, Andrew

    2016-01-01

    Stress has a critical role in the development and expression of many psychiatric disorders, and is a defining feature of posttraumatic stress disorder (PTSD). Stress also limits the efficacy of behavioral therapies aimed at limiting pathological fear, such as exposure therapy. Here we examine emerging evidence that stress impairs recovery from trauma by impairing fear extinction, a form of learning thought to underlie the suppression of trauma-related fear memories. We describe the major structural and functional abnormalities in brain regions that are particularly vulnerable to stress, including the amygdala, prefrontal cortex, and hippocampus, which may underlie stress-induced impairments in extinction. We also discuss some of the stress-induced neurochemical and molecular alterations in these brain regions that are associated with extinction deficits, and the potential for targeting these changes to prevent or reverse impaired extinction. A better understanding of the neurobiological basis of stress effects on extinction promises to yield novel approaches to improving therapeutic outcomes for PTSD and other anxiety and trauma-related disorders. PMID:26105142

  15. Relationship between the partial molar and molar quantity of a thermodynamic state function in a multicomponent mixture – revisited

    International Nuclear Information System (INIS)

    Näfe, H.

    2013-01-01

    As far as a multicomponent mixture is concerned, different versions exist in the literature for the relationship between the partial molar and molar quantity of a thermodynamic state function with the most prominent example of the two quantities being the activity coefficient of an arbitrary component and the excess Gibbs free energy of a mixture comprising this component. Since the relationships published so far have to a large degree been derived independently of each other and result from apparently conflicting approaches, they are still considered as separate subjects in the literature. It is demonstrated that despite this curious situation all relationships are equivalent to each other from a mathematical point of view

  16. Biological Extinction in Earth History

    Science.gov (United States)

    Raup, David M.

    1986-03-01

    Virtually all plant and animal species that have ever lived on the earth are extinct. For this reason alone, extinction must play an important role in the evolution of life. The five largest mass extinctions of the past 600 million years are of greatest interest, but there is also a spectrum of smaller events, many of which indicate biological systems in profound stress. Extinction may be episodic at all scales, with relatively long periods of stability alternating with short-lived extinction events. Most extinction episodes are biologically selective, and further analysis of the victims and survivors offers the greatest chance of deducing the proximal causes of extinction. A drop in sea level and climatic change are most frequently invoked to explain mass extinctions, but new theories of collisions with extraterrestrial bodies are gaining favor. Extinction may be constructive in a Darwinian sense or it may only perturb the system by eliminating those organisms that happen to be susceptible to geologically rare stresses.

  17. Biological extinction in earth history

    Science.gov (United States)

    Raup, D. M.

    1986-01-01

    Virtually all plant and animal species that have ever lived on the earth are extinct. For this reason alone, extinction must play an important role in the evolution of life. The five largest mass extinctions of the past 600 million years are of greatest interest, but there is also a spectrum of smaller events, many of which indicate biological systems in profound stress. Extinction may be episodic at all scales, with relatively long periods of stability alternating with short-lived extinction events. Most extinction episodes are biologically selective, and further analysis of the victims and survivors offers the greatest chance of deducing the proximal causes of extinction. A drop in sea level and climatic change are most frequently invoked to explain mass extinctions, but new theories of collisions with extraterrestrial bodies are gaining favor. Extinction may be constructive in a Darwinian sense or it may only perturb the system by eliminating those organisms that happen to be susceptible to geologically rare stresses.

  18. Interstellar dust and extinction

    International Nuclear Information System (INIS)

    Mathis, J.S.

    1990-01-01

    It is noted that the term interstellar dust refers to materials with rather different properties, and that the mean extinction law of Seaton (1979) or Savage and Mathis (1979) should be replaced by the expression given by Cardelli et al. (1989), using the appropriate value of total-to-selective extinction. The older laws were appropriate for the diffuse ISM but dust in clouds differs dramatically in its extinction law. Dust is heavily processed while in the ISM by being included within clouds and cycled back into the diffuse ISM many times during its lifetime. Hence, grains probably reflect only a trace of their origin, although meteoritic inclusions with isotopic anomalies demonstrate that some tiny particles survive intact from a supernova origin to the present. 186 refs

  19. Switchgrass leaf area index and light extinction coefficients

    Science.gov (United States)

    Biomass production simulation modeling for plant species is often dependent upon accurate simulation or measurement of canopy light interception and radiation use efficiency. With the recent interest in converting large tracts of land to biofuel species cropping, modeling vegetative yield with grea...

  20. Fusion of mandibular third molar with supernumerary fourth molar

    OpenAIRE

    López Carriches, C.; Leco Berrocal, I.; Baca Pérez-Bryan, R.

    2008-01-01

    La fusión dental es la unión de dos gérmenes dentales normalmente separados, mientras que la geminación se define como el intento de división de un único germen dental. La fusión y geminación de molares es poco frecuente en la dentición permanente. Describimos un caso clínico de un tercer molar inferior derecho fusionado a un cuarto molar supernumerario en un paciente varón de 36 años que ha presentado repetidos episodios de pericoronaritis. Tras el estudio radiológico se realiza la exodoncia...

  1. Extinction of sodium fires

    International Nuclear Information System (INIS)

    Malet, J.C.; Spagna, F.

    1989-01-01

    This paper presents how, starting from a knowledge of sodium ignition and burning, principles for extinction (smothering catch trays, leak recuperation systems, powders) can be developed. These techniques applied in Superphenix 1 and PEC reactors have been tested in the ESMERALDA experimental program which is a joint French/Italian project. (author)

  2. Radiographic assessment of third molars development and it's relation to dental and chronological age in an Iranian population.

    Science.gov (United States)

    Monirifard, Mohamad; Yaraghi, Navid; Vali, Ava; Vali, Asana; Vali, Amrita

    2015-01-01

    The aim of the present study was to estimate chronological age based on third molar development and to determine the association between dental age and third molar calcification stages. In this cross-sectional study, 505 digital panoramic radiographs of 223 males (44.2%) and 282 females (55.8%) between the age of 6 and 17 were selected from patients who were treated in Departments of Pediatrics and Orthodontics of Isfahan University of Medical Sciences between the years of 2009 and 2013. Correlation between chronological age and third molar development was analyzed with SPSS 21 using Spearman's Rank correlation coefficient, Chi-square test and multiple regression statistical tests (P third molars demonstrated a highly significant correlation with dental age (P age were mandibular left third molar in males and mandibular right third molar in females (r s = 0.072). When multiple regression was used to predict dental age based on molar calcification stage, the only significant correlation was between maxillary left third molar in males (P third molars in females. Relationship between chronological age and molars development stage was significant in all age subgroups and in both gender (P third molars and dental age in males. Results showed that third molar calcification stage can be used as an age predictor and in general mandibular teeth seems to be more reliable for this purpose in both genders and in all ages.

  3. Image analysis of the eruptive positions of third molars and adjacent second molars as indicators of age evaluation in Thai patients.

    Science.gov (United States)

    Mahasantipiya, Phattaranant May; Pramojanee, Sakarat; Thaiupathump, Trasapong

    2013-12-01

    This study was performed to determine the relationship between the stage of tooth eruption (both vertical and mesio-angular) and chronological age. Indirect digital panoramic radiographs were used to measure the distances from the dentinoenamel junction (DEJ) of the second molars to the occlusal plane of the second molar teeth and of the adjacent third molars in 264 Thai males and 437 Thai females using ImageJ software. The ratio of those distances was calculated by patient age, and the correlation coefficient of the ratio of the third molar length to the second molar length was calculated. The correlation between the height of the vertically erupted upper third molar teeth and age was at the intermediate level. The age range of ≥15 to age determined from the eruptional height and actual chronological age was statistically significant. The mean age of the female subjects, in which the position of the right upper third molar teeth was at or above the DEJ of the adjacent second molar but below one half of its coronal height was 19.9±2.6 years. That for the left side was 20.2±2.7 years. The mean ages of the male subjects were 20.1±3.3 years and 19.8±2.7 years for the right and left sides, respectively. It might be possible to predict chronological age from the eruption height of the wisdom teeth.

  4. Endodontic management of a mandibular third molar fused with a fourth molar.

    Science.gov (United States)

    Turell, I L; Zmener, O

    1999-05-01

    Developmental anomalies in permanent molars frequently require surgical intervention. A case of a mandibular third molar fused with a fourth molar which was successfully treated with conservative endodontic therapy is reported.

  5. Metapopulation extinction risk: dispersal's duplicity.

    Science.gov (United States)

    Higgins, Kevin

    2009-09-01

    Metapopulation extinction risk is the probability that all local populations are simultaneously extinct during a fixed time frame. Dispersal may reduce a metapopulation's extinction risk by raising its average per-capita growth rate. By contrast, dispersal may raise a metapopulation's extinction risk by reducing its average population density. Which effect prevails is controlled by habitat fragmentation. Dispersal in mildly fragmented habitat reduces a metapopulation's extinction risk by raising its average per-capita growth rate without causing any appreciable drop in its average population density. By contrast, dispersal in severely fragmented habitat raises a metapopulation's extinction risk because the rise in its average per-capita growth rate is more than offset by the decline in its average population density. The metapopulation model used here shows several other interesting phenomena. Dispersal in sufficiently fragmented habitat reduces a metapopulation's extinction risk to that of a constant environment. Dispersal between habitat fragments reduces a metapopulation's extinction risk insofar as local environments are asynchronous. Grouped dispersal raises the effective habitat fragmentation level. Dispersal search barriers raise metapopulation extinction risk. Nonuniform dispersal may reduce the effective fraction of suitable habitat fragments below the extinction threshold. Nonuniform dispersal may make demographic stochasticity a more potent metapopulation extinction force than environmental stochasticity.

  6. Galactic dust and extinction

    International Nuclear Information System (INIS)

    Lyngaa, G.

    1979-01-01

    The ratio R between visual extinction and colour excess, is slightly larger than 3 and does not vary much throughout our part of the Galaxy. The distribution of dust in the galactic plane shows, on the large scale, a gradient with higher colour excesses towards l=50 0 than towards l=230 0 . On the smaller scale, much of the dust responsible for extinction is situated in clouds which tend to group together. The correlation between positions of interstellar dust clouds and positions of spiral tracers seems rather poor in our Galaxy. However, concentrated dark clouds as well as extended regions of dust show an inclined distribution similar to the Gould belt of bright stars. (Auth.)

  7. Analysis of extinction properties as a function of relative humidity using a κ-EC-Mie model in Nanjing

    Directory of Open Access Journals (Sweden)

    Z. Zhang

    2017-03-01

    coefficient in Nanjing was due to particles in the 0.2–1.0 µm size range. Under dry conditions, the higher mass fraction of particles in the 0.2–1.0 µm size range caused the higher extinction coefficient. An increase in RH led to a significant increase in the extinction coefficient, although the increases differed among the different size segments. For λ = 550 nm, the extinction coefficient from the 0.01–0.2, 0.2–0.5, and 1.0–2.0 µm size ranges increased significantly with the increase in RH, whereas the extinction contributions from the 0.5–1.0 and 2.0–10.0 µm size ranges to the extinction coefficient decreased slightly.

  8. The effect of experimental resolution on crystal reflectivity and secondary extinction in neutron diffraction

    DEFF Research Database (Denmark)

    Dietrich, O.W.; Als-Nielsen, Jens Aage

    1965-01-01

    The reflectivity for neutrons of a plane slab crystal is calculated in the transmission case when the crystal is placed between two Seller collimators. The calculations indicate that the crystal reflectivity, as well as the secondary extinction coefficient, depends signicantly on the angular...... resolution of the collimators. Curves are given for the extinction of the crystal with different crystal and collimator parameters....

  9. Molar development in sheep: morphology, radiography, microhardness

    International Nuclear Information System (INIS)

    Milhaud, G.; Nezit, J.

    1991-01-01

    The chronology of molar development is studied from radiographic and macroscopic observations on 48 south Pre-Alps were living under optimal nutritional conditions. It was found that the first molar started its development in utero, the second molar at one month after birth, and the third molar, at 9-10 months. The first molar emerged into the oral cavity at 3 months, the second at 9 months and the third molar at 18 months. The first molar began the development of its roots at 6-7 months, the second molar at 11-12 months and the third molar at 20-22 months. The first molar reached completion of the growth of its roots at 3.5-4 years, the second and the third molars at about 6 years. The molars show the particularity of being functional during the three months which follow their eruption although the development of the crown is not completed. Then the accelerated wear is only partially compensated by the growth of the roots. The study also shows how the combined effects of wear and dentine deposit in the pulp cavity affect the morphology of molars. It reveals the marked hardness of enamel (240 Vickers units) and the low resistance of dentine at the surface of attrition (30 Vickers units)

  10. Hypomineralized Second Primary Molars as Predictor of Molar Incisor Hypomineralization

    Science.gov (United States)

    Negre-Barber, A.; Montiel-Company, J. M.; Boronat-Catalá, M.; Catalá-Pizarro, M.; Almerich-Silla, J. M.

    2016-01-01

    Molar incisor hypomineralization (MIH) is a developmental defect of dental enamel that shares features with hypomineralized second primary molars (HSPM). Prior to permanent tooth eruption, second primary molars could have predictive value for permanent molar and incisor hypomineralization. To assess this possible relationship, a cross-sectional study was conducted in a sample of 414 children aged 8 and 9 years from the INMA cohort in Valencia (Spain). A calibrated examiner (linear-weighted Kappa 0.83) performed the intraoral examinations at the University of Valencia between November 2013 and 2014, applying the diagnostic criteria for MIH and HSPM adopted by the European Academy of Paediatric Dentistry. 100 children (24.2%) presented MIH and 60 (14.5%) presented HSPM. Co-occurrence of the two defects was observed in 11.1% of the children examined. The positive predictive value was 76.7% (63.9–86.6) and the negative predictive value 84.7% (80.6–88.3). The positive likelihood ratio (S/1-E) was 10.3 (5.9–17.9) and the negative likelihood ratio (1-S/E) 0.57 (0.47–0.68). The odds ratio was 18.2 (9.39–35.48). It was concluded that while the presence of HSPM can be considered a predictor of MIH, indicating the need for monitoring and control, the absence of this defect in primary dentition does not rule out the appearance of MIH. PMID:27558479

  11. Light extinction in metallic powder beds: Correlation with powder structure

    International Nuclear Information System (INIS)

    Rombouts, M.; Froyen, L.; Gusarov, A.V.; Bentefour, E.H.; Glorieux, C.

    2005-01-01

    A theoretical correlation between the effective extinction coefficient, the specific surface area, and the chord length distribution of powder beds is verified experimentally. The investigated powder beds consist of metallic particles of several tens of microns. The effective extinction coefficients are measured by a light-transmission technique at a wavelength of 540 nm. The powder structure is characterized by a quantitative image analysis of powder bed cross sections resulting in two-point correlation functions and chord length distributions. The specific surface area of the powders is estimated by laser-diffraction particle-size analysis and by the two-point correlation function. The theoretically predicted tendency of increasing extinction coefficient with specific surface area per unit void volume is confirmed by the experiments. However, a significant quantitative discrepancy is found for several powders. No clear correlation of the extinction coefficient with the powder material and particle size, and morphology is revealed, which is in line with the assumption of geometrical optics

  12. Extinction of radiant energy by large atmospheric crystals with different shapes

    International Nuclear Information System (INIS)

    Shefer, Olga

    2016-01-01

    The calculated results of extinction characteristics of visible and infrared radiation for large semi-transparent crystals are obtained by hybrid technique, which is a combination of the geometric optics method and the physical optics method. Energy and polarization characteristics of the radiation extinction in terms of the elements of the extinction matrix for individual large crystals and ensemble of crystals are discussed. Influences of particle shapes, aspect ratios, parameters of size distribution, complex refractive index, orientation of crystals, wavelength, and the polarization state of an incident radiation on the extinction are illustrated. It is shown that the most expressive and stable features of energy and polarization characteristics of the extinction are observed in the midinfrared region, despite the fact that the ice particles significantly absorb the radiant energy of this spectrum. It is demonstrated that the polarized extinction characteristics can reach several tens of percent at IR wavelengths. For the large crystals, the conditions of occurrence of the spectral behavior of the extinction coefficient in the visible, near-IR, and mid-IR wavelength ranges are determined. - Highlights: • Method of physical optics is used at coherent sum of diffracted and refracted fields. • The extinction characteristics in terms of elements of extinction matrix are obtained. • Influence of shapes and sizes of large particles on the extinction is evaluated. • Conditions of occurrence of extinction features are determined.

  13. Fracture behavior of human molars.

    Science.gov (United States)

    Keown, Amanda J; Lee, James J-W; Bush, Mark B

    2012-12-01

    Despite the durability of human teeth, which are able to withstand repeated loading while maintaining form and function, they are still susceptible to fracture. We focus here on longitudinal fracture in molar teeth-channel-like cracks that run along the enamel sidewall of the tooth between the gum line (cemento-enamel junction-CEJ) and the occlusal surface. Such fractures can often be painful and necessitate costly restorative work. The following study describes fracture experiments made on molar teeth of humans in which the molars are placed under axial compressive load using a hard indenting plate in order to induce longitudinal cracks in the enamel. Observed damage modes include fractures originating in the occlusal region ('radial-median cracks') and fractures emanating from the margin of the enamel in the region of the CEJ ('margin cracks'), as well as 'spalling' of enamel (the linking of longitudinal cracks). The loading conditions that govern fracture behavior in enamel are reported and observations made of the evolution of fracture as the load is increased. Relatively low loads were required to induce observable crack initiation-approximately 100 N for radial-median cracks and 200 N for margin cracks-both of which are less than the reported maximum biting force on a single molar tooth of several hundred Newtons. Unstable crack growth was observed to take place soon after and occurred at loads lower than those calculated by the current fracture models. Multiple cracks were observed on a single cusp, their interactions influencing crack growth behavior. The majority of the teeth tested in this study were noted to exhibit margin cracks prior to compression testing, which were apparently formed during the functional lifetime of the tooth. Such teeth were still able to withstand additional loading prior to catastrophic fracture, highlighting the remarkable damage containment capabilities of the natural tooth structure.

  14. Modelling interstellar extinction: Pt. 1

    International Nuclear Information System (INIS)

    Jones, A.P.

    1988-01-01

    Several methods of calculating the extinction of porous silicate grains are discussed, these include effective medium theories and hollow spherical shells. Porous silicate grains are shown to produce enhanced infrared, ultraviolet and far-ultraviolet extinction and this effect can be used to reduce the abundance of carbon required to match the average interstellar extinction, however, matching the visual extinction is rather more problematical. We have shown that the enhanced extinction at long and short wavelengths have different origins, and have explained why the visual extinction is little affected by porosity. The implications of porous grains in the interstellar medium are discussed with particular reference to surface chemistry, the polarization of starlight, and their dynamical evolution. (author)

  15. Extinction Events Can Accelerate Evolution

    DEFF Research Database (Denmark)

    Lehman, Joel; Miikkulainen, Risto

    2015-01-01

    Extinction events impact the trajectory of biological evolution significantly. They are often viewed as upheavals to the evolutionary process. In contrast, this paper supports the hypothesis that although they are unpredictably destructive, extinction events may in the long term accelerate...... evolution by increasing evolvability. In particular, if extinction events extinguish indiscriminately many ways of life, indirectly they may select for the ability to expand rapidly through vacated niches. Lineages with such an ability are more likely to persist through multiple extinctions. Lending...... computational support for this hypothesis, this paper shows how increased evolvability will result from simulated extinction events in two computational models of evolved behavior. The conclusion is that although they are destructive in the short term, extinction events may make evolution more prolific...

  16. Rescuing Ecosystems from Extinction Cascades

    Science.gov (United States)

    Sahasrabudhe, Sagar; Motter, Adilson

    2010-03-01

    Food web perturbations stemming from climate change, overexploitation, invasive species, and natural disasters often cause an initial loss of species that results in a cascade of secondary extinctions. Using a predictive modeling framework, here we will present a systematic network-based approach to reduce the number of secondary extinctions. We will show that the extinction of one species can often be compensated by the concurrent removal of a second specific species, which is a counter-intuitive effect not previously tested in complex food webs. These compensatory perturbations frequently involve long-range interactions that are not a priori evident from local predator-prey relationships. Strikingly, in numerous cases even the early removal of a species that would eventually be extinct by the cascade is found to significantly reduce the number of cascading extinctions. Other nondestructive interventions based on partial removals and growth suppression and/or mortality increase are shown to sometimes prevent all secondary extinctions.

  17. Acoustic integrated extinction

    OpenAIRE

    Norris, Andrew N.

    2015-01-01

    The integrated extinction (IE) is defined as the integral of the scattering cross section as a function of wavelength. Sohl et al. (2007 J. Acoust. Soc. Am. 122, 3206–3210. (doi:10.1121/1.2801546)) derived an IE expression for acoustic scattering that is causal, i.e. the scattered wavefront in the forward direction arrives later than the incident plane wave in the background medium. The IE formula was based on electromagnetic results, for which scattering is causal by default. Here, we der...

  18. Mass extinctions of Earth

    International Nuclear Information System (INIS)

    Fernandez, B.; Fernandez, P.; Pereira, B.

    2015-01-01

    Throughout the history of our planet, there have been global phenomena which have led to the disappearance of a large number of species: It is what is known as mass or massive extinctions. This article will make a tour of these large events, from the most remote antiquity to the present day. Today we find ourselves immersed in a process unprecedented since we are eyewitnesses and, more important still, an active part in the decision-making process to try to mitigate their effects. (Author)

  19. Mass extinctions and supernova explosions

    OpenAIRE

    Korschinek, Gunther

    2016-01-01

    A nearby supernova (SN) explosion could have negatively influenced life on Earth, maybe even been responsible for mass extinctions. Mass extinction poses a significant extinction of numerous species on Earth, as recorded in the paleontologic, paleoclimatic, and geological record of our planet. Depending on the distance between the Sun and the SN, different types of threats have to be considered, such as ozone depletion on Earth, causing increased exposure to the Sun's ultraviolet radiation, o...

  20. Extinction of H II regions

    International Nuclear Information System (INIS)

    Israel, F.P.; Kennicutt, R.C.

    1980-01-01

    Visual extinction of H II regions in nine nearby galaxies as derived from the ratio of the radio continuum emission to H-alpha emission is systematically larger than visual extinction deduced from the Balmer lines alone, if one assumes a value Av/E(B-V) 3. An optically-limited sample of about 30 extragalactic H II regions has a mean extinction of 1.7 m in the visual while about 1.2 m is not seen in the reddening of the Balmer lines. Both reddening and extinction decreases with increasing galactic radius, at least for M33 and M101

  1. A reconciliation of extinction theories

    International Nuclear Information System (INIS)

    Sabine, T.M.

    1988-01-01

    The differences between previous theoretical treatments of extinction based on the Darwin intensity equations arise because of the different functional form chosen for the coupling constant σ. When the same function is used these theories make closely similar predictions. It is shown that a limiting condition on integrated intensity as the crystal size increases puts restrictions on the functions which may be used. A Lorentzian or Fresnellian function can be used for primary extinction while secondary extinction requires a Gaussian, rectangular or triangular function. An analytical expression is given for the variation in the value of the extinction factor with scattering angle. (orig.)

  2. CANINE ECTOPIC TREATMENT WITH FIRST MOLAR EXTRACTION

    Directory of Open Access Journals (Sweden)

    Angelica Margo

    2015-06-01

    Full Text Available Decision to extract or not and the type of tooth must be analyzed carefully in orthodontic treatment. Preferable tooth to be extracted was the tooth with large caries or restoration. Usually the type of tooth to be extracted was second molar (if the third molar appears, incisor, first molar, and combination of several teeth. Orthodontic treatment with molar extraction is more difficult to treat and the result is usually compromise. There are several considerations in extracting first molar such as tooth with large caries or restoration, hypoplasia, periapical disease, large discrepancy, high maxilla-mandibular plane angle, and cases with anterior open bite. Nowadays, orthodontic cases with molar extraction do not prolong the treatment time compared to premolar extraction case, but the anchorage system must be considered carefully. The present case was treated with extraction of first molar to solve anterior crowding with maximum anchorage at the upper jaw and using Nance Holding Appliance.

  3. Phenomenon of primary and secondary extinction in textured material

    International Nuclear Information System (INIS)

    Kryshtab, T.G.; Palacios G, J.; Mazin, M.O.

    2002-01-01

    A new X-ray diffraction method is proposed for a more exact calculation of pole figures to determine the crystallite orientation distribution function (CODF) in textured materials, by the introduction of a correction of the integrated intensity of the diffracted beam due to the phenomenon of extinction. Besides, for the case of a symmetrical Bragg reflection from an ''infinitely thick'' flat parallel plate textured sample a simple solution is developed for the problem of separation and determination of primary and secondary extinction parameters, which can be present simultaneously. The determination of these parameters gives additional information about crystallite structure and allows us to evaluate the average subgrains size and their disorientation, respectively. In this work according to the dynamic diffraction theory, it is shown that the extinction length, which is directly connected with the phenomenon of primary extinction, in the Bragg geometry for σ polarization (perpendicular) is independent on the wavelength used for a given reflection. On the other hand, the additional contribution from secondary extinction depends on X-ray wavelength due to the change of effective absorption coefficient. Considering this fact, the calculations of pole density and the parameters of primary and secondary extinction are performed using the same strong reflection for two different wavelengths and, for one of these wavelengths, a second order of reflection. For confirmation of the proposed method a partially cold rolled aluminium sample and an aluminium powder standard sample were measured. The corrected pole densities, the values of primary and secondary extinction and the average sizes of perfect coherent areas and average angle of disorientation of subgrains in the selected directions were obtained. The obtained results show that the precise X-ray diffraction characterization of textured materials requires the consideration, in general, of primary as well as secondary

  4. Global extinction in spiral galaxies

    NARCIS (Netherlands)

    Tully, RB; Pierce, MJ; Saunders, W; Verheijen, MAW; Witchalls, PL

    Magnitude-limited samples of spiral galaxies drawn from the Ursa Major and Pisces Clusters are used to determine their extinction properties as a function of inclination. Imaging photometry is available for 87 spirals in the B, R, I, and K' bands. Extinction causes systematic scatter in

  5. Evolution: Postponing Extinction by Polyandry

    OpenAIRE

    Wade, Michael J.

    2010-01-01

    Sex-ratio meiotic drive occurs when males produce a predominance of X-chromosome bearing sperm and an inordinate number of daughters. A driving X causes highly female-biased sex ratios and the risk of extinction. Polyandry can rescue a population from extinction.

  6. Optimising Extinction of Conditioned Disgust

    NARCIS (Netherlands)

    Bosman, Renske C.; Borg, Charmaine; de Jong, Peter J.

    2016-01-01

    Maladaptive disgust responses are tenacious and resistant to exposure-based interventions. In a similar vein, laboratory studies have shown that conditioned disgust is relatively insensitive to Conditioned Stimulus (CS)-only extinction procedures. The relatively strong resistance to extinction might

  7. Expressly fabricated molar tube bases: enhanced adhesion.

    Science.gov (United States)

    Sharma, Tarun; Phull, Tarun Singh; Rana, Tarun; Kumar, Varun

    2014-06-01

    Clinicians, Orthodontists and their patients' parents often expect the best results in the shortest time span possible. Orthodontic bonding of molar tubes has been an acceptable risk in a modern era of refined biomaterials and instrumentation. Although many orthodontists still prefer banding to bonding, it is the failure rate of the tubes on molars which accounts to an impedance in molar bonding. One of the reasons for molar attachment failures is attributed to improper adaptation of the buccal tube base with or without increased thickness of composite. Merits of banding the second molars especially when these are the terminal teeth for anchorage have been overemphasized in the literature. The present article presents a simple and relatively less time consuming technique of preparing molar tubes to be bonded on tooth surfaces which may be quite difficult to isolate especially for bonding, for example, mandibular second molars. The increased surface area of the composite scaffold helps not only in enhanced bond strength but also serves to reduce the incidence of plaque accumulation given the dexterity of invitro preparation. The removal of the occlusal part of the molar tube scaffold helps in prevention of open / raised bite tendencies. The present innovation, therefore, is not merely serendipity but a structured technique to overcome a common dilemma for the clinical orthodontist. The present dictum of banding being superior to molar tube bonding may prove to be futile with trendsetting molar attachments. It is also an established fact that bonding proves to be a lesser expensive modality when compared to banding procedures.

  8. Behavioral tagging of extinction learning.

    Science.gov (United States)

    de Carvalho Myskiw, Jociane; Benetti, Fernando; Izquierdo, Iván

    2013-01-15

    Extinction of contextual fear in rats is enhanced by exposure to a novel environment at 1-2 h before or 1 h after extinction training. This effect is antagonized by administration of protein synthesis inhibitors anisomycin and rapamycin into the hippocampus, but not into the amygdala, immediately after either novelty or extinction training, as well as by the gene expression blocker 5,6-dichloro-1-beta-D-ribofuranosylbenzimidazole administered after novelty training, but not after extinction training. Thus, this effect can be attributed to a mechanism similar to synaptic tagging, through which long-term potentiation can be enhanced by other long-term potentiations or by exposure to a novel environment in a protein synthesis-dependent fashion. Extinction learning produces a tag at the appropriate synapses, whereas novelty learning causes the synthesis of plasticity-related proteins that are captured by the tag, strengthening the synapses that generated this tag.

  9. Extinction of Harrington's mountain goat

    International Nuclear Information System (INIS)

    Mead, J.I.; Martin, P.S.; Euler, R.C.; Long, A.; Jull, A.J.T.; Toolin, L.J.; Donahue, D.J.; Linick, T.W.

    1986-01-01

    Keratinous horn sheaths of the extinct Harrington's mountain goat, Oreamnos harringtoni, were recovered at or near the surface of dry caves of the Grand Canyon, Arizona. Twenty-three separate specimens from two caves were dated nondestructively by the tandem accelerator mass spectrometer (TAMS). Both the TAMS and the conventional dates indicate that Harrington's mountain goat occupied the Grand Canyon for at least 19,000 years prior to becoming extinct by 11,160 +/- 125 radiocarbon years before present. The youngest average radiocarbon dates on Shasta ground sloths, Nothrotheriops shastensis, from the region are not significantly younger than those on extinct mountain goats. Rather than sequential extinction with Harrington's mountain goat disappearing from the Grand Canyon before the ground sloths, as one might predict in view of evidence of climatic warming at the time, the losses were concurrent. Both extinctions coincide with the regional arrival of Clovis hunters

  10. Extinction of metal fires

    International Nuclear Information System (INIS)

    Mellottee, H.

    1977-01-01

    The main points of a large bibliography on liquid and solid metal fires are set out. The various methods used to fight these fires are presented; covering by powders is specially emphasized. Since this method has promising results, the various possible techniques, extinction by cooling the metal, by blanketing, by formation of a continuous insulating layer (by fusion or pyrolysis of a powder) or by a surface reaction between powder and metal are studied. The conditions of conservation and use of powders are outlined, then the various powders are described: inert powders, powders undergoing a physical transformation (fusion or vitrification of an organic compound, fusion of eutectic inorganic mixtures), multiple effect powders. Precise examples are quoted [fr

  11. Measuring Extinction with ALE

    Science.gov (United States)

    Zimmer, Peter C.; McGraw, J. T.; Gimmestad, G. G.; Roberts, D.; Stewart, J.; Smith, J.; Fitch, J.

    2007-12-01

    ALE (Astronomical LIDAR for Extinction) is deployed at the University of New Mexico's (UNM) Campus Observatory in Albuquerque, NM. It has begun a year-long testing phase prior deployment at McDonald Observatory in support of the CCD/Transit Instrument II (CTI-II). ALE is designed to produce a high-precision measurement of atmospheric absorption and scattering above the observatory site every ten minutes of every moderately clear night. LIDAR (LIght Detection And Ranging) is the VIS/UV/IR analog of radar, using a laser, telescope and time-gated photodetector instead of a radio transmitter, dish and receiver. In the case of ALE -- an elastic backscatter LIDAR -- 20ns-long, eye-safe laser pulses are launched 2500 times per second from a 0.32m transmitting telescope co-mounted with a 50mm short-range receiver on an alt-az mounted 0.67m long-range receiver. Photons from the laser pulse are scattered and absorbed as the pulse propagates through the atmosphere, a portion of which are scattered into the field of view of the short- and long-range receiver telescopes and detected by a photomultiplier. The properties of a given volume of atmosphere along the LIDAR path are inferred from both the altitude-resolved backscatter signal as well as the attenuation of backscatter signal from altitudes above it. We present ALE profiles from the commissioning phase and demonstrate some of the astronomically interesting atmospheric information that can be gleaned from these data, including, but not limited to, total line-of-sight extinction. This project is funded by NSF Grant 0421087.

  12. Osmotic and apparent molar properties of binary mixtures alcohol + 1-butyl-3-methylimidazolium trifluoromethanesulfonate ionic liquid

    International Nuclear Information System (INIS)

    González, Emilio J.; Calvar, Noelia; Domínguez, Ángeles; Macedo, Eugénia A.

    2013-01-01

    Highlights: ► Osmotic and physical properties of binary mixtures {alcohol + [BMim][TfO]} were measured. ► From experimental data, apparent molar properties and osmotic coefficients were calculated. ► The apparent properties were fitted using a Redlich–Meyer type equation. ► The osmotic coefficients were correlated using the Extended Pitzer model. -- Abstract: In this work, physical properties (densities and speeds of sound) for the binary systems {1-propanol, or 2-propanol, or 1-butanol, or 2-butanol, or 1-pentanol + 1-butyl-3-methylimidazolium trifluoromethanesulfonate} were experimentally measured from T = (293.15 to 323.15) K and at atmospheric pressure. These data were used to calculate the apparent molar volume and apparent molar isentropic compression which were fitted to a Redlich–Meyer type equation. This fit was used to obtain the corresponding apparent molar properties at infinite dilution. On the other hand, the osmotic and activity coefficients and vapor pressures of these binary mixtures were also determined at T = 323.15 K using the vapor pressure osmometry technique. The Extended Pitzer model of Archer was employed to correlate the experimental osmotic coefficients. From the parameters obtained in the correlation, the mean molal activity coefficients and the excess Gibbs free energy for the studied mixtures were calculated

  13. External and internal anatomy of third molars.

    Science.gov (United States)

    Guerisoli, D M; de Souza, R A; de Sousa Neto, M D; Silva, R G; Pécora, J D

    1998-01-01

    The external and internal anatomy of 269 third molars (155 maxillary and 114 mandibular) were studied. The teeth were measured, classified according to their root number and shape and the internal anatomy was observed by the use of diaphanization. A great anatomical variability was found, with the presence of up to 5 roots in maxillary third molars and 3 roots in mandibular third molars. The number of root canals followed the same pattern.

  14. Pulpectomy procedures in primary molar teeth

    OpenAIRE

    Hany Mohamed Aly Ahmed

    2014-01-01

    Premature loss of primary molars can cause a number of undesirable consequences including loss of arch length, insufficient space for erupting premolars and mesial tipping of the permanent molars. Pulpectomy of primary molar teeth is considered as a reasonable treatment approach to ensure either normal shedding or a long-term survival in instances of retention. Despite being a more conservative treatment option than extraction, efficient pulpectomy of bizarre and tortuous root canals encased ...

  15. Selection in a subdivided population with local extinction and recolonization.

    Science.gov (United States)

    Cherry, Joshua L

    2003-01-01

    In a subdivided population, local extinction and subsequent recolonization affect the fate of alleles. Of particular interest is the interaction of this force with natural selection. The effect of selection can be weakened by this additional source of stochastic change in allele frequency. The behavior of a selected allele in such a population is shown to be equivalent to that of an allele with a different selection coefficient in an unstructured population with a different size. This equivalence allows use of established results for panmictic populations to predict such quantities as fixation probabilities and mean times to fixation. The magnitude of the quantity N(e)s(e), which determines fixation probability, is decreased by extinction and recolonization. Thus deleterious alleles are more likely to fix, and advantageous alleles less likely to do so, in the presence of extinction and recolonization. Computer simulations confirm that the theoretical predictions of both fixation probabilities and mean times to fixation are good approximations. PMID:12807797

  16. Permanent molars: Delayed development and eruption

    Directory of Open Access Journals (Sweden)

    Arathi R

    2006-05-01

    Full Text Available Delayed development and eruption of all the permanent molars is a rare phenomenon, which can cause disturbance in the developing occlusion. The eruption of permanent first and second molars is very important for the coordination of facial growth and for providing sufficient occlusal support for undisturbed mastication. In the case described, the first permanent molars were delayed in their development and were seen erupting at the age of nine and a half years. Severe disparity between the left and the right side of the dentition with respect to the rate of development of molars were also present.

  17. Dental lesions and restorative treatment in molars

    Directory of Open Access Journals (Sweden)

    Gheorghiu Irina-Maria

    2017-08-01

    Full Text Available This article review specific clinical issues of the molar teeth, as well as the therapeutic approach of their pathology. The dental pathology we face in the group of molars is related to: dental caries, dental trauma (crown and crown-root fractures, dental wear phenomena. The therapeutic approach of the molar teeth is represented by: restoration of the loss of hard dental tissues; endodontic treatments of pulpal and periapical complications; surgical treatment. The restorative treatments in molars are: direct restorations, with or without supplementary anchorage for obturations; inlay, onlay; prosthetic crown.

  18. Genetic sex determination and extinction.

    Science.gov (United States)

    Hedrick, Philip W; Gadau, Jürgen; Page, Robert E

    2006-02-01

    Genetic factors can affect the probability of extinction either by increasing the effect of detrimental variants or by decreasing the potential for future adaptive responses. In a recent paper, Zayed and Packer demonstrate that low variation at a specific locus, the complementary sex determination (csd) locus in Hymenoptera (ants, bees and wasps), can result in a sharply increased probability of extinction. Their findings illustrate situations in which there is a feedback process between decreased genetic variation at the csd locus owing to genetic drift and decreased population growth, resulting in an extreme type of extinction vortex for these ecologically important organisms.

  19. Incidence of root canal treatment of second molars following adjacent impacted third molar extraction

    Directory of Open Access Journals (Sweden)

    Yener Oguz

    2016-03-01

    Conclusion: Although the incidence is minimal, iatrogenic subluxation injuries occurring during the surgical removal of impacted third molars can lead to pulpal complications and a requirement for root canal treatment of adjacent second molars.

  20. Image analysis of the eruptive positions of third molars and adjacent second molars as indicators of age evaluation in Thai patients

    International Nuclear Information System (INIS)

    Mahasantipiya, Phattaranant May; Pramojanee, Sakarat; Thaiupathump, Trasapong

    2013-01-01

    This study was performed to determine the relationship between the stage of tooth eruption (both vertical and mesio-angular) and chronological age. Indirect digital panoramic radiographs were used to measure the distances from the dentinoenamel junction (DEJ) of the second molars to the occlusal plane of the second molar teeth and of the adjacent third molars in 264 Thai males and 437 Thai females using ImageJ software. The ratio of those distances was calculated by patient age, and the correlation coefficient of the ratio of the third molar length to the second molar length was calculated. The correlation between the height of the vertically erupted upper third molar teeth and age was at the intermediate level. The age range of ≥15 to <16 years was noted to be the range in which the correlation between the chronological age determined from the eruptional height and actual chronological age was statistically significant. The mean age of the female subjects, in which the position of the right upper third molar teeth was at or above the DEJ of the adjacent second molar but below one half of its coronal height was 19.9±2.6 years. That for the left side was 20.2±2.7 years. The mean ages of the male subjects were 20.1±3.3 years and 19.8±2.7 years for the right and left sides, respectively. It might be possible to predict chronological age from the eruption height of the wisdom teeth.

  1. Image analysis of the eruptive positions of third molars and adjacent second molars as indicators of age evaluation in Thai patients

    Energy Technology Data Exchange (ETDEWEB)

    Mahasantipiya, Phattaranant May; Pramojanee, Sakarat; Thaiupathump, Trasapong [Chiang Mai University, Chiang Mai (Thailand)

    2013-12-15

    This study was performed to determine the relationship between the stage of tooth eruption (both vertical and mesio-angular) and chronological age. Indirect digital panoramic radiographs were used to measure the distances from the dentinoenamel junction (DEJ) of the second molars to the occlusal plane of the second molar teeth and of the adjacent third molars in 264 Thai males and 437 Thai females using ImageJ software. The ratio of those distances was calculated by patient age, and the correlation coefficient of the ratio of the third molar length to the second molar length was calculated. The correlation between the height of the vertically erupted upper third molar teeth and age was at the intermediate level. The age range of ≥15 to <16 years was noted to be the range in which the correlation between the chronological age determined from the eruptional height and actual chronological age was statistically significant. The mean age of the female subjects, in which the position of the right upper third molar teeth was at or above the DEJ of the adjacent second molar but below one half of its coronal height was 19.9±2.6 years. That for the left side was 20.2±2.7 years. The mean ages of the male subjects were 20.1±3.3 years and 19.8±2.7 years for the right and left sides, respectively. It might be possible to predict chronological age from the eruption height of the wisdom teeth.

  2. Mini implant supported molar tubes: A novel method for attaching the molar tubes

    Directory of Open Access Journals (Sweden)

    Nitin V Muralidhar

    2017-01-01

    Full Text Available Banding or bonding procedures have been the only means of attaching molar tubes onto the permanent molar teeth till date in the field of orthodontics. This clinical innovation aims to include the use of mini implant for the purpose of attaching the molar tubes thereby eliminating the iatrogenic effects of banding and bonding of the teeth.

  3. Reconsidering the extinction of ichthyosaurs

    OpenAIRE

    Fischer, Valentin

    2010-01-01

    Despite their extreme adaptation to life in open sea, ichthyosaurs were one of the first major groups of post-Triassic marine reptiles to disappear, at the end of Cenomanian, whereas plesiosaurs, mosasaurs and numerous families of marine crocodiles and sea turtles disappeared during the Cretaceous/Paleocene Extinction Event. It has been proposed that unique biological factors drove ichthyosaurs to extinction, namely a break in the food chain at the level of belemnites or a progressive ecologi...

  4. The Sixth Great Mass Extinction

    Science.gov (United States)

    Wagler, Ron

    2012-01-01

    Five past great mass extinctions have occurred during Earth's history. Humanity is currently in the midst of a sixth, human-induced great mass extinction of plant and animal life (e.g., Alroy 2008; Jackson 2008; Lewis 2006; McDaniel and Borton 2002; Rockstrom et al. 2009; Rohr et al. 2008; Steffen, Crutzen, and McNeill 2007; Thomas et al. 2004;…

  5. Morphologic study of the maxillary molars. Part II: Internal anatomy.

    Science.gov (United States)

    Pécora, J D; Woelfel, J B; Sousa Neto, M D; Issa, E P

    1992-01-01

    The internal anatomy of three hundred and seventy (370) decalcified and cleared human maxillary molars was studied. Seventy-five percent of the first molars, 58% of the second molars and 68% of the third molars studied presented three (3) root canals and 25% of the first molars, 42% of the second molars and 32% of the third molars presented four (4) root canals. The authors observed that the incidence of two root canals in the mesiobuccal root was higher in second maxillary molars than in first maxillary molars.

  6. Association between Peritonsillar Abscess and Molar Caries

    Directory of Open Access Journals (Sweden)

    M Shayani Nasab

    2006-05-01

    Full Text Available Background: Peritonsillar abscess is the most common deep neck infections that are related with periodontal disease which has the same pathogenesis. We determined the relationship between peritonsillar infection and molar caries. Methods: In a cross-sectional study, 33 consecutive patients whom referred to Hamadan university clinic of otolaryngologic for peritonsillar abscess were examined by otolaryngologist and dentist who investigated relationship between peritonsillar infection and molar caries. Results: There were 27 males and 6 females with mean age 26.7+_7 years. The frequency caries on ipsilateral peritonsillar infection sides was in relation to molars caries on opposite sides (conterol group. This corrolation was significant with odds ratio 2.5. Conclusion: Molar caries were seen 2.5 times more likely to have peritonsillar infection compared with normal molar sides. Key Words: Peritonsillar abscess, Infection, Periodontal disease, Dental caries

  7. Activity coefficients from molecular simulations using the OPAS method

    Science.gov (United States)

    Kohns, Maximilian; Horsch, Martin; Hasse, Hans

    2017-10-01

    A method for determining activity coefficients by molecular dynamics simulations is presented. It is an extension of the OPAS (osmotic pressure for the activity of the solvent) method in previous work for studying the solvent activity in electrolyte solutions. That method is extended here to study activities of all components in mixtures of molecular species. As an example, activity coefficients in liquid mixtures of water and methanol are calculated for 298.15 K and 323.15 K at 1 bar using molecular models from the literature. These dense and strongly interacting mixtures pose a significant challenge to existing methods for determining activity coefficients by molecular simulation. It is shown that the new method yields accurate results for the activity coefficients which are in agreement with results obtained with a thermodynamic integration technique. As the partial molar volumes are needed in the proposed method, the molar excess volume of the system water + methanol is also investigated.

  8. Thermal Transgressions and Phanerozoic Extinctions

    Science.gov (United States)

    Worsley, T. R.; Kidder, D. L.

    2007-12-01

    A number of significant Phanerozoic extinctions are associated with marine transgressions that were probably driven by rapid ocean warming. The conditions associated with what we call thermal transgressions are extremely stressful to life on Earth. The Earth system setting associated with end-Permian extinction exemplifies an end-member case of our model. The conditions favoring extreme warmth and sea-level increases driven by thermal expansion are also conducive to changes in ocean circulation that foster widespread anoxia and sulfidic subsurface ocean waters. Equable climates are characterized by reduced wind shear and weak surface ocean circulation. Late Permian and Early Triassic thermohaline circulation differs considerably from today's world, with minimal polar sinking and intensified mid-latitude sinking that delivers sulfate from shallow evaporative areas to deeper water where it is reduced to sulfide. Reduced nutrient input to oceans from land at many of the extinction intervals results from diminished silicate weathering and weakened delivery of iron via eolian dust. The falloff in iron-bearing dust leads to minimal nitrate production, weakening food webs and rendering faunas and floras more susceptible to extinction when stressed. Factors such as heat, anoxia, ocean acidification, hypercapnia, and hydrogen sulfide poisoning would significantly affect these biotas. Intervals of tectonic quiescence set up preconditions favoring extinctions. Reductions in chemical silicate weathering lead to carbon dioxide buildup, oxygen drawdown, nutrient depletion, wind and ocean current abatement, long-term global warming, and ocean acidification. The effects of extinction triggers such as large igneous provinces, bolide impacts, and episodes of sudden methane release are more potent against the backdrop of our proposed preconditions. Extinctions that have characteristics we call for in the thermal transgressions include the Early Cambrian Sinsk event, as well as

  9. The influence of premature loss of temporary upper molars on permanent molars.

    Science.gov (United States)

    Cernei, E R; Maxim, Dana Cristiana; Zetu, Irina Nicoleta

    2015-01-01

    Premature loss of primary molars due to dental caries and their complications has been associated with space loss and eruptive difficulties, especially when the loss occurs early. The aim of our study was to determine the impact of premature loss of temporary upper molars upon the longitudinal axis of the first and second upper permanent molar. The study group included 64 patients 6-9 years old with premature loss of primary molars and a control group of 48 patients with intact temporary teeth. It was evaluated the angle between longitudinal axis of first and second upper permanent molars and occlusal plane. The sofware used is Easy Dent 4 Viewer®.The data were analyzed by using the Statistical Package for the Social Sciences (version 20.0; SPSS, Chicago, III). It was observed that premature loss of upper second deciduous molars modifies greater the vertical axis of the permanent molars than the premature loss of first upper primary molar. First upper primary molar loss cause an acceleration eruption of first premolar, which will produce a distal inclintion of the both permanent molars. The use of space maintainers after premature loss of the second upper temporary molar is a last solution in preventing tridimensional lesions in the dental arch and occlusion.

  10. Maxillary second molar impaction in the adjacent ectopic third molar: Report of five rare cases

    Science.gov (United States)

    Souki, Bernardo Q.; Cheib, Paula L.; de Brito, Gabriela M.; Pinto, Larissa S. M. C.

    2015-01-01

    Maxillary second molar impaction in the adjacent ectopic third molar is a rare condition that practitioners might face in the field of pediatric dentistry and orthodontics. The early diagnosis and extraction of the adjacent ectopic third molar have been advocated, and prior research has reported a high rate of spontaneous eruption following third molar removal. However, some challenges in the daily practice are that the early diagnosis of this type of tooth impaction is difficult with conventional radiographic examination, and sometimes the early surgical removal of the maxillary third molar must be postponed because of the risks of damaging the second molar. The objective of this study is to report a case series of five young patients with maxillary second molar impaction and to discuss the difficulty of early diagnosis with the conventional radiographic examination, and unpredictability of self-correction. PMID:26321848

  11. Maxillary second molar impaction in the adjacent ectopic third molar: Report of five rare cases

    Directory of Open Access Journals (Sweden)

    Bernardo Q Souki

    2015-01-01

    Full Text Available Maxillary second molar impaction in the adjacent ectopic third molar is a rare condition that practitioners might face in the field of pediatric dentistry and orthodontics. The early diagnosis and extraction of the adjacent ectopic third molar have been advocated, and prior research has reported a high rate of spontaneous eruption following third molar removal. However, some challenges in the daily practice are that the early diagnosis of this type of tooth impaction is difficult with conventional radiographic examination, and sometimes the early surgical removal of the maxillary third molar must be postponed because of the risks of damaging the second molar. The objective of this study is to report a case series of five young patients with maxillary second molar impaction and to discuss the difficulty of early diagnosis with the conventional radiographic examination, and unpredictability of self-correction.

  12. Experimental excess molar properties of binary mixtures of (3-amino-1-propanol + isobutanol, 2-propanol) at T = (293.15 to 333.15) K and modelling the excess molar volume by Prigogine–Flory–Patterson theory

    International Nuclear Information System (INIS)

    Kermanpour, F.; Niakan, H.Z.

    2012-01-01

    Highlights: ► Density and viscosity of binary mixtures of propanol derivatives were measured at T = (293.15 to 333.15) K. ► The excess molar properties were calculated from these experimental data and correlated by Redlich–Kister equation. ► The PFP model was applied for correlating the excess molar volumes. - Abstract: Density and viscosity of binary mixtures of (x 1 3-amino-1-propanol + x 2 isobutanol) and (x 1 3-amino-1-propanol + x 2 2-propanol) were measured over the entire composition range and from temperatures (293.15 to 333.15) K at ambient pressure. The excess molar volumes and viscosity deviations were calculated and correlated by the Redlich–Kister (RK) equation. The thermal expansion coefficient and its excess value, isothermal coefficient of excess molar enthalpy, and excess partial molar volumes were determined by using the experimental values of density and are described as a function of composition and temperature. The excess molar volumes are negative over the entire mole fraction range for both mixtures and increase with increasing temperature. The excess molar volumes obtained were correlated by the Prigogine–Flory–Patterson (PFP) model. The viscosity deviations of the binary mixtures are negative over the entire composition range and decrease with increasing temperature.

  13. Treating Intraradicular Pockets of molars

    Directory of Open Access Journals (Sweden)

    H. Lotfizade

    1987-10-01

    Full Text Available It appears that until bone graft has not achieved 100% success, intraradicular diseases remain controversial and therefore, different treatment plans are suggested for them. Treating intraradicular diseases depend on many factors: maxillary molars are more prone to bone loss and have worse prognosis. To assess prognosis more carefully these factors should be considered: 1 bone loss: its apical depth, local or generalized 2 bone condition: buccal, lingual, mesial and distal aspects 3 tooth mobility: grades 2 and 3 have not good prognosis. Crown root ratio is also important. 4 the angle of divergence of roots: the more the roots are divergent, the better the prognosis would be. 5adjacent teeth health 6tooth position in jaws 7 age and general health of the patients 8 oral hygiene In general, teeth with 2 roots can be treated more effectively than 3 root ones. Maxillary first premolars are exceptions that do not respond to the treatments positively. We should look forward to the future investigations and findings.

  14. Rare occurrence of the left maxillary horizontal third molar impaction ...

    African Journals Online (AJOL)

    Rare occurrence of the left maxillary horizontal third molar impaction, the right maxillary third molar vertical impaction and the left mandibular third molar vertical impaction with inferior alveolar nerve proximity in a 30 year old female: a case report.

  15. Fusión de un tercer molar mandibular con un cuarto molar supernumerario Fusion of mandibular third molar with supernumerary fourth molar

    Directory of Open Access Journals (Sweden)

    C. López Carriches

    2008-10-01

    Full Text Available La fusión dental es la unión de dos gérmenes dentales normalmente separados, mientras que la geminación se define como el intento de división de un único germen dental. La fusión y geminación de molares es poco frecuente en la dentición permanente. Describimos un caso clínico de un tercer molar inferior derecho fusionado a un cuarto molar supernumerario en un paciente varón de 36 años que ha presentado repetidos episodios de pericoronaritis. Tras el estudio radiológico se realiza la exodoncia del cordal semiincluido bajo anestesia local. Llevamos a cabo una revisión bibliográfica al respecto.Dental fusion is the union of two tooth buds that normally are separated, while gemination is defined as an attempt by a single tooth bud to divide. The fusion and gemination of molars is uncommon in permanent teeth. We report a clinical case of a right lower third molar fused to a supernumerary fourth molar in a 36-year-old male patient with repeated episodes of inflammation. After the radiologic study, the semi-impacted third molar was extracted under local anesthesia. The literature was reviewed.

  16. Autogenous transplantation of maxillary and mandibular molars.

    Science.gov (United States)

    Reich, Peter P

    2008-11-01

    Autogenous tooth transplantation has been used as a predictable surgical approach to correct malocclusion and replace edentulous areas. This article focuses on the surgical approach and technique for molar transplantation. Thirty-two patients aged between 11 and 25 years underwent 44 autogenous molar transplantations. The procedure involved transplantation of impacted or newly erupted third molars into the extraction sockets of nonrestorable molars and surgical removal and replacement of horizontally impacted molars into their proper vertical alignment. Five basic procedural concepts were applied: 1) atraumatic extraction, avoiding disruption of the root sheath and root buds; 2) apical contouring of bone at the transplantation site and maxillary sinus lift via the Summers osteotome technique, when indicated, for maxillary molars; 3) preparation of a 4-wall bony socket; 4) avoidance of premature occlusal interferences; and 5) stabilization of the tooth with placement of a basket suture. All 32 patients successfully underwent the planned procedure. To date, 2 patients have had localized infection that resulted in loss of the transplant. The remaining 42 transplants remain asymptomatic and functioning, with a mean follow-up period of 19 months. No infection, ankylosis, loss of the transplant, or root resorption has been noted. In addition, endodontic therapy has not been necessary on any transplanted teeth. Autogenous tooth transplantation has been discussed and described in the literature previously, with a primary focus on cuspid and bicuspid transplantation. The molar transplant is infrequently discussed in today's literature, possibly because of the preponderance of titanium dental implants. Autogenous molar transplantation is a viable procedure with low morbidity and excellent functional and esthetic outcomes. This report shows the successful transplantation of 42 of 44 molars in 32 patients with a mean follow-up period of 19 months.

  17. Estudio de mezclas de disolventes orgánicos y triglicéridos de aceite de linaza o los ácidos grasos libres. I.- Volumen molar, refracción molar y viscosidad dinámica

    Directory of Open Access Journals (Sweden)

    Mantell Serrano, C.

    1995-06-01

    Full Text Available Measurements of molar volume, refraction index and dynamic viscosity in mixtures of fatty acids or triglycerides and trichloroethylene, tetrachloroethylene and hexane were realized. Temperature range studied was 278-313 K each 5 K. The relationship between molar volume and molar fraction show high correlation coefficient In fatty acids with trichloroethylene and tetrachloroethylene mixtures. On the other hand, hexane mixtures show little contractions of molar volume at low molar fractions. Triglyceride mixtures present important deviations with regard to the ideality of the molar volume. The adjusts obtained for the molar volume values versus temperature are acceptable, calculating the coefficients of thermal expansion of the studied mixtures. Equally, the adjust of the experimental results of viscosity for two prediction equations are studied: one of additive type and the other of parabolic type.

    Se han realizado medidas del volumen molar, índice de refracción y viscosidad dinámica en el intervalo de temperatura de 278 K a 313 K cada 5 K, a mezclas de ácidos grasos o triglicéridos con tricloroetileno, tetracloroetileno y hexano. Las mezclas de ácidos grasos con tricloroetileno y tetracloroetileno, presentan unos altos coeficientes de correlación para los valores del volumen molar frente a la fracción molar, mientras que las mezclas con hexano, a fracciones molares bajas, manifiestan una pequeña contracción del volumen molar. Las mezclas de triglicéridos presentan importantes desviaciones con respecto a la Idealidad del volumen molar. Los ajustes obtenidos para los valores del volumen molar frente a la temperatura son aceptables, determinándose los valores del coeficiente de dilatación volumétrica a presión constante de las mezclas estudiadas. Igualmente se ha estudiado el ajuste de los resultados experimentales de viscosidad a dos ecuaciones de predicción: una del tipo aditiva y otra del tipo parabólico.

  18. The extinction of the dinosaurs.

    Science.gov (United States)

    Brusatte, Stephen L; Butler, Richard J; Barrett, Paul M; Carrano, Matthew T; Evans, David C; Lloyd, Graeme T; Mannion, Philip D; Norell, Mark A; Peppe, Daniel J; Upchurch, Paul; Williamson, Thomas E

    2015-05-01

    Non-avian dinosaurs went extinct 66 million years ago, geologically coincident with the impact of a large bolide (comet or asteroid) during an interval of massive volcanic eruptions and changes in temperature and sea level. There has long been fervent debate about how these events affected dinosaurs. We review a wealth of new data accumulated over the past two decades, provide updated and novel analyses of long-term dinosaur diversity trends during the latest Cretaceous, and discuss an emerging consensus on the extinction's tempo and causes. Little support exists for a global, long-term decline across non-avian dinosaur diversity prior to their extinction at the end of the Cretaceous. However, restructuring of latest Cretaceous dinosaur faunas in North America led to reduced diversity of large-bodied herbivores, perhaps making communities more susceptible to cascading extinctions. The abruptness of the dinosaur extinction suggests a key role for the bolide impact, although the coarseness of the fossil record makes testing the effects of Deccan volcanism difficult. © 2014 The Authors. Biological Reviews © 2014 Cambridge Philosophical Society.

  19. Estudio de volumen molar y refracción molar de miscelas de triglicéridos (triacetina, tributirina o tricaprilina y alcoholes (etanol, 1-butanol o 1-hexanol

    Directory of Open Access Journals (Sweden)

    Rodríguez Rodríguez, M.

    1992-12-01

    Full Text Available Values of molar refraction for every studied mixtures show linear plots versus molar fractions of triglyceride. Values of molar volume show this behaviour, but only for tributyrin-butanol or tricaprylin-butanol miscellas. However, in tributyrin-ethanol mixtures, volume contractions have been found, whereas triacetin-butanol and tributyrin-hexanol show volume expansions. These facts are related to the mode of being structured of the alcohol and triglyceride molecules in mixtures. A linear relationship between molar volume and temperature have been found, and also a linear dependence between the coefficient of thermal expansion at constant pressure and the molar fraction of triglyceride.

    Los valores de la refracción molar en todas las miscelas estudiadas presentan variaciones lineales frente a la fracción molar de triglicérido. la misma variación que presentan los valores del volumen molar de las miscelas tributirina y tricaprilina en butanol. Sin embargo, en las miscelas de tributirina-etanol se encuentran contracciones de volumen mientras que en las de triacetina-butanol y tributirina-hexanol expansiones, atribuidas en ambos casos a la forma de estructurarse las moléculas de alcohol y triglicérido en las miscelas. Por otra parte, se encuentra una variación lineal entre el volumen molar de las miscelas y la temperatura, y se establece una relación lineal entre el coeficiente de dilatación térmico molar a presión constante y la fracción molar de triglicérido en los cinco sistemas estudiados.

  20. The Component Slope Linear Model for Calculating Intensive Partial Molar Properties: Application to Waste Glasses

    International Nuclear Information System (INIS)

    Reynolds, Jacob G.

    2013-01-01

    Partial molar properties are the changes occurring when the fraction of one component is varied while the fractions of all other component mole fractions change proportionally. They have many practical and theoretical applications in chemical thermodynamics. Partial molar properties of chemical mixtures are difficult to measure because the component mole fractions must sum to one, so a change in fraction of one component must be offset with a change in one or more other components. Given that more than one component fraction is changing at a time, it is difficult to assign a change in measured response to a change in a single component. In this study, the Component Slope Linear Model (CSLM), a model previously published in the statistics literature, is shown to have coefficients that correspond to the intensive partial molar properties. If a measured property is plotted against the mole fraction of a component while keeping the proportions of all other components constant, the slope at any given point on a graph of this curve is the partial molar property for that constituent. Actually plotting this graph has been used to determine partial molar properties for many years. The CSLM directly includes this slope in a model that predicts properties as a function of the component mole fractions. This model is demonstrated by applying it to the constant pressure heat capacity data from the NaOH-NaAl(OH 4 H 2 O system, a system that simplifies Hanford nuclear waste. The partial molar properties of H 2 O, NaOH, and NaAl(OH) 4 are determined. The equivalence of the CSLM and the graphical method is verified by comparing results detennined by the two methods. The CSLM model has been previously used to predict the liquidus temperature of spinel crystals precipitated from Hanford waste glass. Those model coefficients are re-interpreted here as the partial molar spinel liquidus temperature of the glass components

  1. Treatment of ectopic first permanent molar teeth.

    LENUS (Irish Health Repository)

    Hennessy, Joe

    2012-11-01

    Ectopic eruption of the first permanent molar is a relatively common occurence in the developing dentition. A range of treatment options are available to the clinician provided that diagnosis is made early. Non-treatment can result in premature exfoliation of the second primary molar, space loss and impaction of the second premolar. This paper will describe the management of ectopic first permanent molars, using clinical examples to illustrate the available treatment options. CLINICAL RELEVANCE: This paper is relevant to every general dental practitioner who treats patients in mixed dentition.

  2. Mini-implant-supported Molar Distalization

    Directory of Open Access Journals (Sweden)

    Amit Goyal

    2012-01-01

    Full Text Available Temporary anchorage devices popularly called mini-implants or miniscrews are the latest addition to an orthodontist′s armamentarium. The following case report describes the treatment of a 16-year-old girl with a pleasant profile, moderate crowding and Angle′s Class II molar relationship. Maxillary molar distalization was planned and mini-implants were used to preserve the anterior anchorage. After 13 months of treatment, Class I molar and canine relation was achieved bilaterally and there was no anterior proclination. Thus, mini-implants provide a viable option to the clinician to carry out difficult tooth movements without any side effects.

  3. Treatment of ectopic first permanent molar teeth.

    Science.gov (United States)

    Hennessy, Joe; Al-Awadhi, E A; Dwyer, Lian O; Leith, Rona

    2012-11-01

    Ectopic eruption of the first permanent molar is a relatively common occurence in the developing dentition. A range of treatment options are available to the clinician provided that diagnosis is made early. Non-treatment can result in premature exfoliation of the second primary molar, space loss and impaction of the second premolar. This paper will describe the management of ectopic first permanent molars, using clinical examples to illustrate the available treatment options. This paper is relevant to every general dental practitioner who treats patients in mixed dentition.

  4. The premature loss of primary first molars: space loss to molar occlusal relationships and facial patterns.

    Science.gov (United States)

    Alexander, Stanley A; Askari, Marjan; Lewis, Patricia

    2015-03-01

    To investigate space changes with the premature loss of primary first molars and their relationship to permanent molar occlusion and facial forms. Two hundred twenty-six participants (ranging in age from 7 years 8 months to 8 years 2 months; 135 female, 91 male) met all inclusion criteria designed to study space loss as a result of the premature loss of the primary first molar. After 9 months, space loss was evaluated in relationship to molar occlusion and facial form. Statistical evaluation was performed with the paired t-test and with a two-way analysis of variance for independent groups. Patients with leptoprosopic facial form and end-on molar occlusions all exhibited a statistically significant difference when compared to controls in terms of space loss (P molar occlusion displayed space loss as well (P molar occlusion displayed space loss in the maxilla (P molar occlusions showed no significant difference in space loss. The relationship between the first permanent molar occlusion and facial form of the child has an influence on the loss of space at the primary first molar site.

  5. AXIAL MODIFICATIONS OF PERMANENT LOWER MOLARS AFTER PREMATURE LOSSES OF TEMPORARY MOLARS.

    Science.gov (United States)

    Cernei, E R; Mavru, R B; Zetu, Irina Nicoleta

    2016-01-01

    The aim of our study was to determine the impact of premature loss of temporary lower molars upon the longitudinal axis of the first and second permanent molars. The study groups included 61 patients, 6-9 year olds with premature loss of primary molars and a control group of 24 patients with intact temporary teeth. We evaluated the angle between longitudinal axis of first and second lower permanent molars and occlusal plane. It was observed that premature loss of lower second deciduous molar modifies more the vertical axis of first and second permanent molars than the premature loss of first lower primary molar. Reducing space occurs mainly through mesial inclination of molars that separates the edentulous breach. Temporary loss of both lower first molars on the same quadrant causes an accelerated eruption of both premolars increasing the prevalence of eruption sequence: "4-5-3-7". The preservation of the occlusal morpho-functional complex using space maintainers mainly when the premature loss of the second primary molars occurs is the best interceptive treatment option.

  6. Infectious Disease, Endangerment, and Extinction

    Science.gov (United States)

    MacPhee, Ross D. E.; Greenwood, Alex D.

    2013-01-01

    Infectious disease, especially virulent infectious disease, is commonly regarded as a cause of fluctuation or decline in biological populations. However, it is not generally considered as a primary factor in causing the actual endangerment or extinction of species. We review here the known historical examples in which disease has, or has been assumed to have had, a major deleterious impact on animal species, including extinction, and highlight some recent cases in which disease is the chief suspect in causing the outright endangerment of particular species. We conclude that the role of disease in historical extinctions at the population or species level may have been underestimated. Recent methodological breakthroughs may lead to a better understanding of the past and present roles of infectious disease in influencing population fitness and other parameters. PMID:23401844

  7. Open-path, closed-path and reconstructed aerosol extinction at a rural site.

    Science.gov (United States)

    Gordon, Timothy D; Prenni, Anthony J; Renfro, James R; McClure, Ethan; Hicks, Bill; Onasch, Timothy B; Freedman, Andrew; McMeeking, Gavin R; Chen, Ping

    2018-04-09

    The Handix Scientific Open-Path Cavity Ringdown Spectrometer (OPCRDS) was deployed during summer 2016 in Great Smoky Mountains National Park (GRSM). Extinction coefficients from the relatively new OPCRDS and from a more well-established extinction instrument agreed to within 7%. Aerosol hygroscopic growth (f(RH)) was calculated from the ratio of ambient extinction measured by the OPCRDS to dry extinction measured by a closed-path extinction monitor (Aerodyne's Cavity Attenuated Phase Shift Particulate Matter Extinction Monitor, CAPS PMex). Derived hygroscopicity (RH 1995 at the same site and time of year, which is noteworthy given the decreasing trend for organics and sulfate in the eastern U.S. However, maximum f(RH) values in 1995 were less than half as large as those recorded in 2016-possibly due to nephelometer truncation losses in 1995. Two hygroscopicity parameterizations were investigated using high time resolution OPCRDS+CAPS PMex data, and the K ext model was more accurate than the γ model. Data from the two ambient optical instruments, the OPCRDS and the open-path nephelometer, generally agreed; however, significant discrepancies between ambient scattering and extinction were observed, apparently driven by a combination of hygroscopic growth effects, which tend to increase nephelometer truncation losses and decrease sensitivity to the wavelength difference between the two instruments as a function of particle size. There was not a statistically significant difference in the mean reconstructed extinction values obtained from the original and the revised IMPROVE (Interagency Monitoring of Protected Visual Environments) equations. On average IMPROVE reconstructed extinction was ~25% lower than extinction measured by the OPCRDS, which suggests that the IMPROVE equations and 24-hr aerosol data are moderately successful in estimating current haze levels at GRSM. However, this conclusion is limited by the coarse temporal resolution and the low dynamic range of

  8. Agenesia de terceros molares en pacientes de la Facultad de Odontología de la UNAM Agenesia of the third molars in patients of the Faculty of Odontology of the National Autonomous University of Mexico

    Directory of Open Access Journals (Sweden)

    Raúl Díaz Pérez

    2008-12-01

    Full Text Available ANTECEDENTES: los terceros molares o serotinos son los últimos dientes en erupcionar; su presencia genera diversas patologías como apiñamiento, pericoronitis y dolor, generalmente por falta de espacio en los maxilares. Según la filogenia humana son considerados dientes en vías de extinción. Cada vez más presentan una erupción retrasada e incluso ausencia por falta de formación. OBJETIVO: determinar la frecuencia de agenesia de terceros molares en pacientes de la Facultad de Odontología de la Universidad Nacíonal Autónoma de México. MÉTODOS: se examinaron 915 ortopantomografías de pacientes de 16 a 24 años y se realizó el diagnóstico de presencia de los terceros molares, se recabó información sociodemográfica y se analizó la asociación con el sexo usando X². RESULTADOS: el 20 % de la muestra presentó agenesia de los 4 terceros molares, 56 % tuvo los 4, y 24 % solo de 1 a 3, además se encontró que el sexo no determina la presencia de los terceros molares (X²= 0,503, p= 0,478. CONCLUSIONES: la frecuencia de agenesia de terceros molares fue del 20 % y esta es independiente del sexo.ANTECEDENTS: the third molars are the last teeth to erupt. Their presence generate diverse pathologies as crowding, pericoronitis and pain, generally due to the lack of space in the maxillae. According to human phylogeny, they are considered teeth on the way to extinction. They present an increasingly delayed eruption and even absence due to lack of formation, OBJECTIVE: to determine the frequency of agenesia of the third molars in patients of the Faculty of Odontology of the National Autonomous University of Mexico. METHODS: 915 orthopantomographies of patients aged 16-24 were examined and the diagnosis of presence of the third molars was made. Sociodemographic information was necessary and the association with sex was analyzed by using X2. RESULTS: 20 % of the sample presented agenesia of the 4 third molars, 56 % had the 4, and 24 % only from

  9. A principle to correlate extreme values of excess thermodynamic functions with partial molar quantities

    Institute of Scientific and Technical Information of China (English)

    尉志武; 刘芸; 周蕊; 薛芳渝

    2001-01-01

    Excess thermodynamic properties are widely used quantitatively for fluids. It was found that at constant temperature and pressure a molar excess quantity of a mutually miscible binary mixture at the extreme points equals the excess partial molar quantities of the two components, i.e.F1E = F2E = FmE , forming a triple cross point. The relationship is hold for properties such as en-thalpy, entropy, Gibbs free energy, and volume, and is applicable for excess functions with multi extreme points. Solutions at extreme points can be referred to as special mixtures. Particularly fora special mixture of Gibbs free energy, activity coefficients of the two components are identical.

  10. A principle to correlate extreme values of excess thermody-namic functions with partial molar quantities

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Excess thermodynamic properties are widely used quantitatively for fluids. It was found that at constant temperature and pressure a molar excess quantity of a mutually miscible binary mixture at the extreme points equals the excess partial molar quantities of the two components, i.e. , forming a triple cross point. The relationship is hold for properties such as enthalpy, entropy, Gibbs free energy, and volume, and is applicable for excess functions with multi extreme points. Solutions at extreme points can be referred to as special mixtures. Particularly for a special mixture of Gibbs free energy, activity coefficients of the two components are identical.

  11. Endodontic therapy for a fused mandibular molar.

    Science.gov (United States)

    Rotstein, I; Moshonov, J; Cohenca, N

    1997-06-01

    Variations in tooth morphology present a clinical challenge when endodontic treatment is required. A case of conservative endodontic therapy for a fused mandibular second and third molar is presented.

  12. A Molar Pregnancy within the Fallopian Tube

    Directory of Open Access Journals (Sweden)

    Laura Allen

    2016-01-01

    Full Text Available Background. Discussion of the incidence of molar pregnancy and ectopic pregnancy. Role of salpingostomy and special considerations for postoperative care. Case. The patient is a 29-year-old G7P4 who presented with vaginal bleeding in the first trimester and was initially thought to have a spontaneous abortion. Ultrasound was performed due to ongoing symptoms and an adnexal mass was noted. She underwent uncomplicated salpingostomy and was later found to have a partial molar ectopic pregnancy. Conclusion. This case illustrates the rare occurrence of a molar ectopic pregnancy. There was no indication of molar pregnancy preoperatively and this case highlights the importance of submitting and reviewing pathological specimens.

  13. Management of large losses of substances molars

    OpenAIRE

    Reynal, Florence

    2016-01-01

    This work aims to compare the different coronary restorative materials used for large tooth losses in primary molars. The first part of this thesis is dedicated to a description of the four main materials used in coronary restorations of molars : amalgam, glass-ionomer cements, resin-based composite and pedodontic crown. The second part is a systematic review of the literature. The aim is to compare the long-term survival rates of different restoration techniques, in order to help the practit...

  14. Microstructure of a tribosphenic molar - comparative analysis

    OpenAIRE

    ŠPOUTIL, František

    2010-01-01

    The proposed thesis concerns in the study of tribosphenic molar, the key apomorphy of mammalian clade, mainly in structure and development of its enamel coat. As the main model species served us European vespertilionid bat Myotis myotis. The aims of this thesis are: (1) to describe structure and microstructure of enamel in tribosphenic molars in detail; (2) to compare it with unicuspid teeth of the same dentition; (3) to describe mineralization process and enamel maturation in insectivorous d...

  15. Maxillary molar distalization with first class appliance.

    Science.gov (United States)

    Ramesh, Namitha; Palukunnu, Biswas; Ravindran, Nidhi; Nair, Preeti P

    2014-02-27

    Non-extraction treatment has gained popularity for corrections of mild-to-moderate class II malocclusion over the past few decades. The distalization of maxillary molars is of significant value for treatment of cases with minimal arch discrepancy and mild class II molar relation associated with a normal mandibular arch and acceptable profile. This paper describes our experience with a 16-year-old female patient who reported with irregularly placed upper front teeth and unpleasant smile. The patient was diagnosed to have angles class II malocclusion with moderate maxillary anterior crowding, deep bite of 4 mm on a skeletal class II base with an orthognathic maxilla and retrognathic mandible and normal growth pattern. She presented an ideal profile and so molar distalization was planned with the first-class appliance. Molars were distalised by 8 mm on the right and left quadrants and class I molar relation achieved within 4 months. The space gained was utilised effectively to align the arch and establish a class I molar and canine relation.

  16. Permittivity, molar volume and crytical phenomena near the lambda-point in liquid 4He

    International Nuclear Information System (INIS)

    Panov, V.I.; Khvostikov, V.A.

    1982-01-01

    The permittivity, molar volume and thermal expansion coefficient at the saturated vapor pressure are measured for liquid helium 4 He in the temperature range from 1.4 to 4.2 K. It is shown that the thermal expansion coefficient at saturated vapor pressure near the lambda-transition can be described with a high degree of accuracy by a logarithmic function. The values of the critical indexes obtained by studying the nature of the divergence of the isobaric thermal expansion coefficient at 1x10sup(-5) Tsub(lambda) and α'=0.000+-0.0025 for T 4 He near the lambda transition

  17. Theory of invasion extinction dynamics in minimal food webs

    Science.gov (United States)

    Haerter, Jan O.; Mitarai, Namiko; Sneppen, Kim

    2018-02-01

    When food webs are exposed to species invasion, secondary extinction cascades may be set off. Although much work has gone into characterizing the structure of food webs, systematic predictions on their evolutionary dynamics are still scarce. Here we present a theoretical framework that predicts extinctions in terms of an alternating sequence of two basic processes: resource depletion by or competitive exclusion between consumers. We first propose a conceptual invasion extinction model (IEM) involving random fitness coefficients. We bolster this IEM by an analytical, recursive procedure for calculating idealized extinction cascades after any species addition and simulate the long-time evolution. Our procedure describes minimal food webs where each species interacts with only a single resource through the generalized Lotka-Volterra equations. For such food webs ex- tinction cascades are determined uniquely and the system always relaxes to a stable steady state. The dynamics and scale invariant species life time resemble the behavior of the IEM, and correctly predict an upper limit for trophic levels as observed in the field.

  18. Mass Extinctions and Supernova Explosions

    Science.gov (United States)

    Korschinek, Gunther

    A nearby supernova (SN) explosion could have negatively influenced life on Earth, maybe even been responsible for mass extinctions. Mass extinction poses a significant extinction of numerous species on Earth, as recorded in the paleontologic, paleoclimatic, and geological record of our planet. Depending on the distance between the Sun and the SN, different types of threats have to be considered, such as ozone depletion on Earth, causing increased exposure to the Sun's ultraviolet radiation or the direct exposure of lethal X-rays. Another indirect effect is cloud formation, induced by cosmic rays in the atmosphere which result in a drop in the Earth's temperature, causing major glaciations of the Earth. The discovery of highly intensive gamma-ray bursts (GRBs), which could be connected to SNe, initiated further discussions on possible life-threatening events in the Earth's history. The probability that GRBs hit the Earth is very low. Nevertheless, a past interaction of Earth with GRBs and/or SNe cannot be excluded and might even have been responsible for past extinction events.

  19. Modeling Population Growth and Extinction

    Science.gov (United States)

    Gordon, Sheldon P.

    2009-01-01

    The exponential growth model and the logistic model typically introduced in the mathematics curriculum presume that a population grows exclusively. In reality, species can also die out and more sophisticated models that take the possibility of extinction into account are needed. In this article, two extensions of the logistic model are considered,…

  20. New theories about ancient extinctions

    Science.gov (United States)

    Spall, H.

    1986-01-01

    The abrupt disappearance of all the dinosaurs about 65 million years ago, along with perhaps half the plant species and other animals, has been one of the great geological mysteries. Clues to the cause of these extinctions have been scarce and open to many interpretations.

  1. Extinction debt on oceanic islands

    DEFF Research Database (Denmark)

    Triantis, Kostas A.; Borges, Paulo A. V.; Ladle, Richard J.

    2010-01-01

    the magnitude of such future extinction events has been hampered by potentially inaccurate assumptions about the slope of species-area relationships, which are habitat- and taxon-specific. We overcome this challenge by applying a method that uses the historical sequence of deforestation in the Azorean Islands...

  2. The currency and tempo of extinction.

    Science.gov (United States)

    Regan, H M; Lupia, R; Drinnan, A N; Burgman, M A

    2001-01-01

    This study examines estimates of extinction rates for the current purported biotic crisis and from the fossil record. Studies that compare current and geological extinctions sometimes use metrics that confound different sources of error and reflect different features of extinction processes. The per taxon extinction rate is a standard measure in paleontology that avoids some of the pitfalls of alternative approaches. Extinction rates reported in the conservation literature are rarely accompanied by measures of uncertainty, despite many elements of the calculations being subject to considerable error. We quantify some of the most important sources of uncertainty and carry them through the arithmetic of extinction rate calculations using fuzzy numbers. The results emphasize that estimates of current and future rates rely heavily on assumptions about the tempo of extinction and on extrapolations among taxa. Available data are unlikely to be useful in measuring magnitudes or trends in current extinction rates.

  3. EARTH SCIENCE: Did Volcanoes Drive Ancient Extinctions?

    Science.gov (United States)

    Kerr, R A

    2000-08-18

    With the publication in recent weeks of two papers on a mass extinction 183 million years ago, researchers can add five suggestive cases to the list of extinctions with known causes. These extinctions coincide with massive outpourings of lava, accompanied by signs that global warming threw the ocean-atmosphere system out of whack. Although no one can yet pin any of these mass extinctions with certainty on the volcanic eruptions, scientists say it's unlikely that they're all coincidences.

  4. An investigation of the interstellar extinction

    International Nuclear Information System (INIS)

    Roche, P.F.; Aitken, D.K.; Melbourne Univ., Point Cook

    1984-01-01

    The 10 μm extinction towards six WC8 or WC9 Wolf-Rayet stars is investigated. All objects show smooth dust emission suffering silicate absorption with depths well correlated with the extinction in the visible. The de-reddened spectra are well represented by emission from featureless grain components, possibly from iron or carbon grains. The extinction to the stars is found to be dominantly interstellar in origin with little extinction from the circumstellar shell. (author)

  5. Molar volume, thermal expansivity and isothermal compressibility of trans-decahydronaphthalene up to 200MPa and 446K

    Institute of Scientific and Technical Information of China (English)

    Zhu Hu-Gang; Liu Zhi-Hua; Tian Yi-Ling; Xue Yuan; Yin Liang

    2005-01-01

    The molar volume isotherms of trans-decahydronaphthalene (C10H18) between 293 and 446 K and at pressures from 10 to 200 MPa have been determined. A modified Tait equation of state is used to fit each experimental molar volume isotherm with a maximum average deviation of 0.029%. The thermal expansivity (cubic expansion coefficient) α and isothermal compressibility κ were determined by fitting the slopes of the isobaric curves and isotherms, respectively.The coefficients in the equation Vm = C1 + C2T + C3T2 - C4p - C5pT have been fitted with an average deviation of 1.03%.

  6. Predicting pathology in impacted mandibular third molars

    Directory of Open Access Journals (Sweden)

    Aveek Mukherji

    2017-01-01

    Full Text Available Introduction: The rising incidence of the impacted mandibular third molars and their association with pathologies is now considered a public health problem. Aims and Objectives: The objective of this study was to assess the position of impacted mandibular third molars that are prone to developing pathologies and to determine the frequency and type of pathological conditions associated with these impacted teeth to facilitate planning for their prophylactic removal. Materials and Methods: Consecutive panoramic radiographs and clinical examination of 300 patients with impacted mandibular third molars were collected. They were segregated according to Pell and Gregory’s classification, Winter’s classification, and according to their state of eruption. These were correlated with associated pathologies based on clinical and radiological criteria. Statistical Analysis Used: Descriptive statistics included computation of percentages, mean, and standard deviations. The statistical test applied for the analysis was Pearson’s Chi-square test (χ2. For this test, confidence interval and P value were set at 93% and ≤0.03, respectively. Results: The pathology most commonly associated with impacted third molars was pericoronitis, which had the highest frequency of occurrence in partially erupted, distoangular, and IA positioned (as per Pell and Gregory classification impacted teeth. Impacted mandibular third molars, which were in IA position, placed mesially, and partially erupted, were prone to develop pathologies such as dental caries and periodontitis. Conclusion: The clinical and radiographical features of impacted third molar may be correlated to the development of their pathological complications. The partially impacted mandibular third molars with mesioangularly aligned in IA position have the highest potential to cause pathological complications.

  7. Further Evidence of Auditory Extinction in Aphasia

    Science.gov (United States)

    Marshall, Rebecca Shisler; Basilakos, Alexandra; Love-Myers, Kim

    2013-01-01

    Purpose: Preliminary research ( Shisler, 2005) suggests that auditory extinction in individuals with aphasia (IWA) may be connected to binding and attention. In this study, the authors expanded on previous findings on auditory extinction to determine the source of extinction deficits in IWA. Method: Seventeen IWA (M[subscript age] = 53.19 years)…

  8. Bilateral maxillary fused second and third molars: a rare occurrence.

    Science.gov (United States)

    Liang, Rui-Zhen; Wu, Jin-Tao; Wu, You-Nong; Smales, Roger J; Hu, Ming; Yu, Jin-Hua; Zhang, Guang-Dong

    2012-12-01

    This case report describes the diagnosis and endodontic therapy of maxillary fused second and third molars, using cone-beam computed tomography (CBCT). A 31-year-old Chinese male, with no contributory medical or family/social history, presented with throbbing pain in the maxillary right molar area following an unsuccessful attempted tooth extraction. Clinical examination revealed what appeared initially to be a damaged large extra cusp on the buccal aspect of the distobuccal cusp of the second molar. However, CBCT revealed that a third molar was fused to the second molar. Unexpectedly, the maxillary left third molar also was fused to the second molar, and the crown of an unerupted supernumerary fourth molar was possibly also fused to the apical root region of the second molar. Operative procedures should not be attempted without adequate radiographic investigation. CBCT allowed the precise location of the root canals of the right maxillary fused molar teeth to permit successful endodontic therapy, confirmed after 6 months.

  9. Dental age assessment of young Iranian adults using third molars: A multivariate regression study.

    Science.gov (United States)

    Bagherpour, Ali; Anbiaee, Najmeh; Partovi, Parnia; Golestani, Shayan; Afzalinasab, Shakiba

    2012-10-01

    In recent years, a noticeable increase in forensic age estimations of living individuals has been observed. Radiologic assessment of the mineralisation stage of third molars is of particular importance, with regard to the relevant age group. To attain a referral database and regression equations for dental age estimation of unaccompanied minors in an Iranian population was the goal of this study. Moreover, determination was made concerning the probability of an individual being over the age of 18 in case of full third molar(s) development. Using the scoring system of Gleiser and Hunt, modified by Köhler, an investigation of a cross-sectional sample of 1274 orthopantomograms of 885 females and 389 males aged between 15 and 22 years was carried out. Using kappa statistics, intra-observer reliability was tested. With Spearman correlation coefficient, correlation between the scores of all four wisdom teeth, was evaluated. We also carried out the Wilcoxon signed-rank test on asymmetry and calculated the regression formulae. A strong intra-observer agreement was displayed by the kappa value. No significant difference (p-value for upper and lower jaws were 0.07 and 0.59, respectively) was discovered by Wilcoxon signed-rank test for left and right asymmetry. The developmental stage of upper right and upper left third molars yielded the greatest correlation coefficient. The probability of an individual being over the age of 18 is 95.6% for males and 100.0% for females in case four fully developed third molars are present. Taking into consideration gender, location and number of wisdom teeth, regression formulae were arrived at. Use of population-specific standards is recommended as a means of improving the accuracy of forensic age estimates based on third molars mineralisation. To obtain more exact regression formulae, wider age range studies are recommended. Copyright © 2012 Elsevier Ltd and Faculty of Forensic and Legal Medicine. All rights reserved.

  10. Oxygen from Hydrogen Peroxide. A Safe Molar Volume-Molar Mass Experiment.

    Science.gov (United States)

    Bedenbaugh, John H.; And Others

    1988-01-01

    Describes a molar volume-molar mass experiment for use in general chemistry laboratories. Gives background technical information, procedures for the titration of aqueous hydrogen peroxide with standard potassium permanganate and catalytic decomposition of hydrogen peroxide to produce oxygen, and a discussion of the results obtained in three…

  11. Does fixed retention prevent overeruption of unopposed mandibular second molars in maxillary first molar extraction cases?

    NARCIS (Netherlands)

    Livas, Christos; Halazonetis, Demetrios J; Booij, Johan W; Katsaros, Christos; Ren, Yijin

    2016-01-01

    BACKGROUND: The objective of this study was to investigate whether multistranded fixed retainers prevented overeruption of unopposed mandibular second molars in maxillary first molar extraction cases. METHODS: The panoramic radiographs of 65 Class II Division 1 Caucasian Whites (28 females, 37

  12. SECOND MOLAR UPRIGHTING AFTER PREMATURE LOSS OF MANDIBULAR FIRST PERMANENT MOLAR--CASE REPORT.

    Science.gov (United States)

    Cernei, E R; Mavru, R B; Zetui, Irina Nicoleta

    2015-01-01

    Uprighting a tipped molar by using an uprighting spring is a fundamental orthodontic treatment technique. Following a weak anchorage done only by the anterior teeth the permanent lower second molar will rotate around its center of resistance, and besides the distalizing movement will occur its extrusion. Following the reaction, the mandibular anterior teeth will have a movement of intrusion. All these elements will lead to anterior open bite. Correction of vertical problems has become easier with the advent of mini-implants. U.I patient aged 24 years presenting for aesthetic and functional disorders. Clinical examination reveals intraoral Class I molar malocclusion on the right sight, upper narrowing arch with a slight overbite, and the both permanent first molars on the left side lost prematurely. The tooth 37 is inclined at 600 degrees to the plane of occlusion. To avoid front opening occlusion we used an orthodontic miniscrew inserted between the canine and the first premolar on the same side to achieve the second molar up righting. Lower second molar uprighting was achieved without unwanted movements in anterior mandibular region and without molar extrusion. Using mini implants in uprighting a tipped molar will achieve the desired tooth movement and will reduce the number of unwanted side effects and eventually to improve patient's esthetics.

  13. Assessment of skeletal maturation using mandibular second molar maturation stages.

    Science.gov (United States)

    Goyal, S; Goyal, S; Gugnani, N

    2014-01-01

    To investigate the relationship between cervical vertebrae maturation and mandibular second molar calcification stages. The study was designed as a retrospective, descriptive and crosssectional research project. Pre-treatment lateral cephalograms and panoramic radiographs of 99 males and 110 females in the age range of 7 to 18 years 7 months were evaluated with Demirjian Index (DI) and cervical vertebrae maturation indicators (CVMI) of Hassel and Farman. A null hypothesis was proposed that there is no relation between CVMI and DI. A highly significant association (Pearson's contingency coefficient 0.713 for males and 0.863 for females) was found between DI and CVMI. In males, the DI stage E corresponded to stage 2 of CVMI (pre-peak of pubertal growth spurt) and DI stages F and G corresponded to stages 3 and 4 of CVMI (peak of pubertal growth spurt). DI stage H was associated with stages 5 and 6 of CVMI (end of pubertal growth spurt). In females, the DI stages C, D corresponded to CVMI stages 1, 2; DI stages E, F with CVMI stages 3, 4; DI stages G, H with CVMI stages 5, 6. Mandibular second molar calcification stages can be used as indicators for assessment of skeletal maturity.

  14. Molar volume of eutectic solvents as a function of molar composition and temperature☆

    Institute of Scientific and Technical Information of China (English)

    Farouq S. Mjalli

    2016-01-01

    The conventional Rackett model for predicting liquid molar volume has been modified to cater for the effect of molar composition of the Deep Eutectic Solvents (DES). The experimental molar volume data for a group of commonly used DES has been used for optimizing the improved model. The data involved different molar compositions of each DES. The validation of the new model was performed on another set of DESs. The average relative deviation of the model on the training and validation datasets was approximately 0.1%while the Rackett model gave a relative deviation of more than 1.6%. The modified model deals with variations in DES molar com-position and temperature in a more consistent way than the original Rackett model which exhibits monotonic performance degradation as temperature moves away from reference conditions. Having the composition of the DES as a model variable enhances the practical utilization of the predicting model in diverse design and process simulation applications.

  15. Ectopic eruption of the maxillary first permanent molar: characteristics and occurrence in growing children.

    Science.gov (United States)

    Barberia-Leache, Elena; Suarez-Clúa, María Cruz; Saavedra-Ontiveros, Dolores

    2005-07-01

    The purpose of this study was to determine the characteristics and occurrence of the ectopic eruption of the maxillary first permanent molar in a sample of growing Spanish children. A descriptive, observational, retrospective study was done using the radiographs of 509 consecutive patients, who were in the first phase of mixed dentition. A method was designed to evaluate the amount of pathologic resorption of the second maxillary primary molar and the impaction of the first permanent molar measured in millimeters. Statistical analysis of the studied variables was done using chi-square, analysis of variance, and Pearson correlation coefficient. The frequency of occurrence was 4.3% with no differences in both sexes. Of these, 36.4% were unilateral and 63.6% bilateral with a right:left relation of 3:1. Of the 36 ectopic molars, 69.4% self-corrected spontaneously. In such cases, the pathological resorption of the root of the second maxillary primary molar and its adverse clinical implications were persistent. The relation between self-correction and impaction was 2.27:1. The average impaction on the right side was 2.91 mm and 1.6 mm on the left side. Correlation between the magnitude of resorption and grade of impaction was not observed. Although resorption was found on grades I and II, spontaneous self-correction could occur without arch length loss. However, on grade III or more, therapeutic intervention has to be done. The benefit of early diagnosis and treatment of the maxillary first permanent molar is the prevention of the premature loss of second maxillary deciduous molar and the resulting malocclusion.

  16. Predicting extinction rates in stochastic epidemic models

    International Nuclear Information System (INIS)

    Schwartz, Ira B; Billings, Lora; Dykman, Mark; Landsman, Alexandra

    2009-01-01

    We investigate the stochastic extinction processes in a class of epidemic models. Motivated by the process of natural disease extinction in epidemics, we examine the rate of extinction as a function of disease spread. We show that the effective entropic barrier for extinction in a susceptible–infected–susceptible epidemic model displays scaling with the distance to the bifurcation point, with an unusual critical exponent. We make a direct comparison between predictions and numerical simulations. We also consider the effect of non-Gaussian vaccine schedules, and show numerically how the extinction process may be enhanced when the vaccine schedules are Poisson distributed

  17. Ångström coefficient as a tracer of the continental aerosols

    NARCIS (Netherlands)

    Kuśmierczyk-Michulec, J.T.; Eijk, A.M.J. van

    2007-01-01

    The variation of the extinction coefficient with wavelength can be presented as a power law function with a constant (related to the power factor) known as the Ångström coefficient. When the particle size distribution is dominated by small particles, usually associated with pollution, the Ångström

  18. Extinction risk escalates in the tropics.

    Directory of Open Access Journals (Sweden)

    Jana C Vamosi

    Full Text Available The latitudinal biodiversity gradient remains one of the most widely recognized yet puzzling patterns in nature. Presently, the high level of extinction of tropical species, referred to as the "tropical biodiversity crisis", has the potential to erode this pattern. While the connection between species richness, extinction, and speciation has long intrigued biologists, these interactions have experienced increased poignancy due to their relevancy to where we should concentrate our conservation efforts. Natural extinction is a phenomenon thought to have its own latitudinal gradient, with lower extinction rates in the tropics being reported in beetles, birds, mammals, and bivalves. Processes that have buffered ecosystems from high extinction rates in the past may also buffer ecosystems against disturbance of anthropogenic origin. While potential parallels between historical and present-day extinction patterns have been acknowledged, they remain only superficially explored and plant extinction patterns have been particularly neglected. Studies on the disappearances of animal species have reached conflicting conclusions, with the rate of extinction appearing either higher or lower in species richness hotspots. Our global study of extinction risk in vascular plants finds disproportionately higher extinction risk in tropical countries, even when indicators of human pressure (GDP, population density, forest cover change are taken into account. Our results are at odds with the notion that the tropics represent a museum of plant biodiversity (places of historically lowered extinction and we discuss mechanisms that may reconcile this apparent contradiction.

  19. Extinction risk escalates in the tropics.

    Science.gov (United States)

    Vamosi, Jana C; Vamosi, Steven M

    2008-01-01

    The latitudinal biodiversity gradient remains one of the most widely recognized yet puzzling patterns in nature. Presently, the high level of extinction of tropical species, referred to as the "tropical biodiversity crisis", has the potential to erode this pattern. While the connection between species richness, extinction, and speciation has long intrigued biologists, these interactions have experienced increased poignancy due to their relevancy to where we should concentrate our conservation efforts. Natural extinction is a phenomenon thought to have its own latitudinal gradient, with lower extinction rates in the tropics being reported in beetles, birds, mammals, and bivalves. Processes that have buffered ecosystems from high extinction rates in the past may also buffer ecosystems against disturbance of anthropogenic origin. While potential parallels between historical and present-day extinction patterns have been acknowledged, they remain only superficially explored and plant extinction patterns have been particularly neglected. Studies on the disappearances of animal species have reached conflicting conclusions, with the rate of extinction appearing either higher or lower in species richness hotspots. Our global study of extinction risk in vascular plants finds disproportionately higher extinction risk in tropical countries, even when indicators of human pressure (GDP, population density, forest cover change) are taken into account. Our results are at odds with the notion that the tropics represent a museum of plant biodiversity (places of historically lowered extinction) and we discuss mechanisms that may reconcile this apparent contradiction.

  20. Rescaling of temporal expectations during extinction

    Science.gov (United States)

    Drew, Michael R.; Walsh, Carolyn; Balsam, Peter D

    2016-01-01

    Previous research suggests that extinction learning is temporally specific. Changing the CS duration between training and extinction can facilitate the loss of the CR within the extinction session but impairs long-term retention of extinction. In two experiments using conditioned magazine approach with rats, we examined the relation between temporal specificity of extinction and CR timing. In Experiment 1 rats were trained on a 12-s, fixed CS-US interval and then extinguished with CS presentations that were 6, 12, or 24 s in duration. The design of Experiment 2 was the same except rats were trained using partial rather than continuous reinforcement. In both experiments, extending the CS duration in extinction facilitated the diminution of CRs during the extinction session, but shortening the CS duration failed to slow extinction. In addition, extending (but not shortening) the CS duration caused temporal rescaling of the CR, in that the peak CR rate migrated later into the trial over the course of extinction training. This migration partially accounted for the faster loss of the CR when the CS duration was extended. Results are incompatible with the hypothesis that extinction is driven by cumulative CS exposure and suggest that temporally extended nonreinforced CS exposure reduces conditioned responding via temporal displacement rather than through extinction per se. PMID:28045291

  1. The contemporary management of third molars.

    Science.gov (United States)

    Hyam, D M

    2018-03-01

    The management of third molars requires a significant assessment and decision process both for the patient and the clinician. The clinician must always identify the indication for third molar surgery, assess the risks of the proposed procedure, and then modify their plan to account for the patient's current and future health, their social and financial setting, and the patient's tolerance of risk. In doing this, the clinician can tailor a solution to meet the individual patient's needs. This decision to remove a third molar is made in the fluid setting of the patient's quality of life and requires regular review. This article gives the clinician the tools, the matrix, and the confidence to guide patients through this process, and outlines some of the pitfalls and common points of bias within the process. © 2018 Australian Dental Association.

  2. Dinasour extinction and volcanic activity

    Science.gov (United States)

    Gledhill, J. A.

    There is at present some controversy about the reason for the mass extinction of dinosaurs and other forms of life at the end of the Cretaceous. A suggestion by Alvarez et al. [1980] that this was due to the collision of the earth with a meteorite 10 km or so in diameter has excited considerable interest [Silver and Schultz, 1982] and also some criticism [Stanley, 1984]. A recent publication [Wood, 1984] describing the catastrophic effects of a relatively minor lava flow in Iceland suggests that intense volcanic activity could have played a large part in the extinctions. In this letter it is pointed out that the Deccan lava flows in India took place in the appropriate time and may well have been of sufficient magnitude to be a major factor in the Cretaceous-Tertiary (C-T) boundary catastrophe.

  3. [Extinction and Reconsolidation of Memory].

    Science.gov (United States)

    Zuzina, A B; Balaban, P M

    2015-01-01

    Retrieval of memory followed by reconsolidation can strengthen a memory, while retrieval followed by extinction results in a decrease of memory performance due to weakening of existing memory or formation of a competing memory. In our study we analyzed the behavior and responses of identified neurons involved in the network underlying aversive learning in terrestrial snail Helix, and made an attempt to describe the conditions in which the retrieval of memory leads either to extinction or reconsolidation. In the network underlying the withdrawal behavior, sensory neurons, premotor interneurons, motor neurons, and modulatory for this network serotonergic neurons are identified and recordings from representatives of these groups were made before and after aversive learning. In the network underlying feeding behavior, the premotor modulatory serotonergic interneurons and motor neurons involved in motor program of feeding are identified. Analysis of changes in neural activity after aversive learning showed that modulatory neurons of feeding behavior do not demonstrate any changes (sometimes a decrease of responses to food was observed), while responses to food in withdrawal behavior premotor interneurons changed qualitatively, from under threshold EPSPs to spike discharges. Using a specific for serotonergic neurons neurotoxin 5,7-DiHT it was shown previously that the serotonergic system is necessary for the aversive learning, but is not necessary for maintenance and retrieval of this memory. These results suggest that the serotonergic neurons that are necessary as part of a reinforcement for developing the associative changes in the network may be not necessary for the retrieval of memory. The hypothesis presented in this review concerns the activity of the "reinforcement" serotonergic neurons that is suggested to be the gate condition for the choice between extinction/reconsolidation triggered by memory retrieval: if these serotonergic neurons do not respond during the

  4. Optimising Extinction of Conditioned Disgust.

    Science.gov (United States)

    Bosman, Renske C; Borg, Charmaine; de Jong, Peter J

    2016-01-01

    Maladaptive disgust responses are tenacious and resistant to exposure-based interventions. In a similar vein, laboratory studies have shown that conditioned disgust is relatively insensitive to Conditioned Stimulus (CS)-only extinction procedures. The relatively strong resistance to extinction might be explained by disgust's adaptive function to motivate avoidance from contamination threats (pathogens) that cannot be readily detected and are invisible to the naked eye. Therefore, the mere visual presentation of unreinforced disgust eliciting stimuli might not be sufficient to correct a previously acquired threat value of the CS+. Following this, the current study tested whether the efficacy of CS-only exposure can be improved by providing additional safety information about the CS+. For the CSs we included two neutral items a pea soup and a sausage roll, whereas for the Unconditioned Stimulus (US) we used one video clip of a woman vomiting and a neutral one about glass blowing. The additional safety information was conveyed by allowing actual contact with the CS+ or by observing an actress eating the food items representing the CS+. When additional safety information was provided via allowing direct contact with the CS+, there was a relatively strong post-extinction increase in participants' willingness-to-eat the CS+. This beneficial effect was still evident at one-week follow up. Also self-reported disgust was lower at one-week follow up when additional safety information was provided. The current findings help explain why disgust is relatively insensitive to CS-only extinction procedures, and provide helpful starting points to improve interventions that are aimed to reduce distress in disgust-related psychopathology.

  5. Optimising Extinction of Conditioned Disgust.

    Directory of Open Access Journals (Sweden)

    Renske C Bosman

    Full Text Available Maladaptive disgust responses are tenacious and resistant to exposure-based interventions. In a similar vein, laboratory studies have shown that conditioned disgust is relatively insensitive to Conditioned Stimulus (CS-only extinction procedures. The relatively strong resistance to extinction might be explained by disgust's adaptive function to motivate avoidance from contamination threats (pathogens that cannot be readily detected and are invisible to the naked eye. Therefore, the mere visual presentation of unreinforced disgust eliciting stimuli might not be sufficient to correct a previously acquired threat value of the CS+. Following this, the current study tested whether the efficacy of CS-only exposure can be improved by providing additional safety information about the CS+. For the CSs we included two neutral items a pea soup and a sausage roll, whereas for the Unconditioned Stimulus (US we used one video clip of a woman vomiting and a neutral one about glass blowing. The additional safety information was conveyed by allowing actual contact with the CS+ or by observing an actress eating the food items representing the CS+. When additional safety information was provided via allowing direct contact with the CS+, there was a relatively strong post-extinction increase in participants' willingness-to-eat the CS+. This beneficial effect was still evident at one-week follow up. Also self-reported disgust was lower at one-week follow up when additional safety information was provided. The current findings help explain why disgust is relatively insensitive to CS-only extinction procedures, and provide helpful starting points to improve interventions that are aimed to reduce distress in disgust-related psychopathology.

  6. Human age estimation combining third molar and skeletal development.

    Science.gov (United States)

    Thevissen, P W; Kaur, J; Willems, G

    2012-03-01

    The wide prediction intervals obtained with age estimation methods based on third molar development could be reduced by combining these dental observations with age-related skeletal information. Therefore, on cephalometric radiographs, the most accurate age-estimating skeletal variable and related registration method were searched and added to a regression model, with age as response and third molar stages as explanatory variable. In a pilot set up on a dataset of 496 (283 M; 213 F) cephalometric radiographs, the techniques of Baccetti et al. (2005) (BA), Seedat et al. (2005) (SE), Caldas et al. (2007) and Rai et al. (2008) (RA) were verified. In the main study, data from 460 (208 F, 224 M) individuals in an age range between 3 and 26 years, for which at the same day an orthopantogram and a cephalogram were taken, were collected. On the orthopantomograms, the left third molar development was registered using the scoring system described by Gleiser and Hunt (1955) and modified by Köhler (1994) (GH). On the cephalograms, cervical vertebrae development was registered according to the BA and SE techniques. A regression model, with age as response and the GH scores as explanatory variable, was fitted to the data. Next, information of BA, SE and BA + SE was, respectively, added to this model. From all obtained models, the determination coefficients and the root mean squared errors were calculated. Inclusion of information from cephalograms based on the BA, as well as the SE, technique improved the amount of explained variance in age acquired from panoramic radiographs using the GH technique with 48%. Inclusion of cephalometric BA + SE information marginally improved the previous result (+1%). The RMSE decreased with 1.93, 1.85 and 2.03 years by adding, respectively, BA, SE and BA + SE information to the GH model. The SE technique allows clinically the fastest and easiest registration of the degree of development of the cervical vertebrae. Therefore, the choice of

  7. Extinction correction and synchrotron radiation

    International Nuclear Information System (INIS)

    Suortti, P.

    1983-01-01

    The primary extinction factor ysub(p) is defined as the ratio of the integrated reflection from a coherently diffracting domain to the integrated kinematical reflection from the same domain. When ysub(p) is larger than 0.5 it may be approximated by ysub(p)= exp[-(αdelta) 2 ], where α is about 0.5 and delta the average size of the coherent domain when measured in units of the extinction length Λ, delta = D/Λ. Transfer equations are applied to symmetrical Laue diffraction, and the reflectivity per unit length, sigma(epsilon) is solved from the measured reflecting ratio as a function of the rocking angle epsilon = theta -thetasub(B). Measurements with conventional x-ray sources are made on single crystal slabs of Be and Si using AgKβ, MoKα 1 and CuKα radiation. The primary extinction factor ysub(p)(epsilon) is solved from a point-by-point comparison of two measurements where the extinction length Λ is changed by varying the polarization and/or wavelength of the x-ray beam. The results show that primary and secondary extinction are strongly correlated, and that the customary assumption of independent size and orientation distributions of crystal mosaics is unjustified. The structure factors for Be and Si show close agreement with other recent measurements and calculations. The limitations of the method are discussed in length, particularly the effects of beam divergences and incoherence of the rays in the crystal. It is concluded that under typical experimental conditions the requirements of the theory are met. Practical limitations arising from the use of characteristic wavelengths and unpolarized radiation prohibit the use of the full potential of the method. The properties of a synchrotron radiation source are compared with a conventional x-ray source, and it is demonstrated that the experimental limitations can be removed by the use of synchrotron radiation. A diffraction experiment with synchrotron radiation is outlined, as well as generalization of the

  8. The (water + acetonitrile) mixture revisited: A new approach for calculating partial molar volumes

    International Nuclear Information System (INIS)

    Carmen Grande, Maria del; Julia, Jorge Alvarez; Barrero, Carmen R.; Marschoff, Carlos M.; Bianchi, Hugo L.

    2006-01-01

    Density and viscosity of (water + acetonitrile) mixtures were measured over the whole composition range at the temperatures: (298.15, 303.15, 308.15, 313.15, and 318.15) K. A new mathematical approach was developed which allows the calculation of the derivatives of density with respect to composition avoiding the appearance of local discontinuities. Thus, reliable partial molar volumes and thermal expansion coefficients were obtained

  9. A notable difference between ideal gas and infinite molar volume limit of van der Waals gas

    Science.gov (United States)

    Liu, Q. H.; Shen, Y.; Bai, R. L.; Wang, X.

    2010-05-01

    The van der Waals equation of state does not sufficiently represent a gas unless a thermodynamic potential with two proper and independent variables is simultaneously determined. The limiting procedures under which the behaviour of the van der Waals gas approaches that of an ideal gas are letting two van der Waals coefficients be zero rather than letting the molar volume become infinitely large; otherwise, the partial derivative of internal energy with respect to pressure at a fixed temperature does not vanish.

  10. A notable difference between ideal gas and infinite molar volume limit of van der Waals gas

    International Nuclear Information System (INIS)

    Liu, Q H; Shen, Y; Bai, R L; Wang, X

    2010-01-01

    The van der Waals equation of state does not sufficiently represent a gas unless a thermodynamic potential with two proper and independent variables is simultaneously determined. The limiting procedures under which the behaviour of the van der Waals gas approaches that of an ideal gas are letting two van der Waals coefficients be zero rather than letting the molar volume become infinitely large; otherwise, the partial derivative of internal energy with respect to pressure at a fixed temperature does not vanish.

  11. Biological correlates of extinction risk in bats.

    Science.gov (United States)

    Jones, Kate E; Purvis, Andy; Gittleman, John L

    2003-04-01

    We investigated patterns and processes of extinction and threat in bats using a multivariate phylogenetic comparative approach. Of nearly 1,000 species worldwide, 239 are considered threatened by the International Union for Conservation of Nature and Natural Resources (IUCN) and 12 are extinct. Small geographic ranges and low wing aspect ratios are independently found to predict extinction risk in bats, which explains 48% of the total variance in IUCN assessments of threat. The pattern and correlates of extinction risk in the two bat suborders are significantly different. A higher proportion (4%) of megachiropteran species have gone extinct in the last 500 years than microchiropteran bats (0.3%), and a higher proportion is currently at risk of extinction (Megachiroptera: 34%; Microchiroptera: 22%). While correlates of microchiropteran extinction risk are the same as in the order as a whole, megachiropteran extinction is correlated more with reproductive rate and less with wing morphology. Bat extinction risk is not randomly distributed phylogenetically: closely related species have more similar levels of threat than would be expected if extinction risk were random. Given the unbalanced nature of the evolutionary diversification of bats, it is probable that the amount of phylogenetic diversity lost if currently threatened taxa disappear may be greater than in other clades with numerically more threatened species.

  12. The ethics of reviving long extinct species.

    Science.gov (United States)

    Sandler, Ronald

    2014-04-01

    There now appears to be a plausible pathway for reviving species that have been extinct for several decades, centuries, or even millennia. I conducted an ethical analysis of de-extinction of long extinct species. I assessed several possible ethical considerations in favor of pursuing de-extinction: that it is a matter of justice; that it would reestablish lost value; that it would create new value; and that society needs it as a conservation last resort. I also assessed several possible ethical arguments against pursuing de-extinction: that it is unnatural; that it could cause animal suffering; that it could be ecologically problematic or detrimental to human health; and that it is hubristic. There are reasons in favor of reviving long extinct species, and it can be ethically acceptable to do so. However, the reasons in favor of pursuing de-extinction do not have to do with its usefulness in species conservation; rather, they concern the status of revived species as scientific and technological achievements, and it would be ethically problematic to promote de-extinction as a significant conservation strategy, because it does not prevent species extinctions, does not address the causes of extinction, and could be detrimental to some species conservation efforts. Moreover, humanity does not have a responsibility or obligation to pursue de-extinction of long extinct species, and reviving them does not address any urgent problem. Therefore, legitimate ecological, political, animal welfare, legal, or human health concerns associated with a de-extinction (and reintroduction) must be thoroughly addressed for it to be ethically acceptable. © 2013 Society for Conservation Biology.

  13. External and internal anatomy of mandibular molars.

    Science.gov (United States)

    Rocha, L F; Sousa Neto, M D; Fidel, S R; da Costa, W F; Pécora, J D

    1996-01-01

    The external and internal anatomy of 628 extracted, mandibular first and second molars was studied. The external anatomy was studied by measuring each tooth and by observing the direction of the root curvatures from the facial surface. The internal anatomy of the pulp cavity was studied by a method of making the teeth translucent.

  14. Polarization extinction ratio of the polarization crosstalk caused by point pressure force in the polarization-maintaining fiber

    Science.gov (United States)

    Mukhtubayev, Azamat B.; Aksarin, Stanislav M.; Strigalev, Vladimir E.

    2017-11-01

    A study of the orthogonal polarization modes crosstalk changes in the point of different mechanical actions (pressure force) in the polarization-maintaining fiber with straining elliptical cladding is presented. It was found that by increasing of the pressure force the polarization extinction ratio increases nonlinearly. Also revealed the dependence of the extinction coefficient and the angle between vector of the mechanical action and polarization axes of the test fiber, which leads to change the extinction coefficient variable from -57 dB to -25 dB under the pressure force of 0.7 N. Also it was found that the cross angle of the fiber axes doesn't influence on the extinction ratio value of the mechanical induced polarization crosstalk.

  15. Extinction debt: a challenge for biodiversity conservation.

    Science.gov (United States)

    Kuussaari, Mikko; Bommarco, Riccardo; Heikkinen, Risto K; Helm, Aveliina; Krauss, Jochen; Lindborg, Regina; Ockinger, Erik; Pärtel, Meelis; Pino, Joan; Rodà, Ferran; Stefanescu, Constantí; Teder, Tiit; Zobel, Martin; Steffan-Dewenter, Ingolf

    2009-10-01

    Local extinction of species can occur with a substantial delay following habitat loss or degradation. Accumulating evidence suggests that such extinction debts pose a significant but often unrecognized challenge for biodiversity conservation across a wide range of taxa and ecosystems. Species with long generation times and populations near their extinction threshold are most likely to have an extinction debt. However, as long as a species that is predicted to become extinct still persists, there is time for conservation measures such as habitat restoration and landscape management. Standardized long-term monitoring, more high-quality empirical studies on different taxa and ecosystems and further development of analytical methods will help to better quantify extinction debt and protect biodiversity.

  16. Temporal specificity of extinction in autoshaping.

    Science.gov (United States)

    Drew, Michael R; Yang, Cynthia; Ohyama, Tatsuya; Balsam, Peter D

    2004-07-01

    Three experiments investigated the effects of varying the conditioned stimulus (CS) duration between training and extinction. Ring doves (Streptopelia risoria) were autoshaped on a fixed CS-unconditioned stimulus (US) interval and extinguished with CS presentations that were longer, shorter, or the same as the training duration. During a subsequent test session, the training CS duration was reintroduced. Results suggest that the cessation of responding during an extinction session is controlled by generalization of excitation between the training and extinction CSs and by the number of nonreinforced CS presentations. Transfer of extinction to the training CS is controlled by the similarity between the extinction and training CSs. Extinction learning is temporally specific. (c) 2004 APA, all rights reserved

  17. Open-field exposure facilitates consummatory extinction.

    Science.gov (United States)

    Justel, Nadia; Psyrdellis, Mariana; Pautassi, Ricardo M

    2016-12-07

    During extinction, the organism learns that a conditioned stimulus or a conditioned response is no longer associated with an unconditioned stimulus, and as a consequence, a decrement in the response is presented. The exposure to novel situations (e.g. exploration of a novel open field) has been used widely to modulate (i.e. either enhance or deteriorate) learning and memory. The aim of the present study was to test whether open-field exposure could modulate consummatory extinction. The results indicated that open-field exposure accelerated the extinction response (i.e. experimental animals provided novelty exposure had lower consummatory behavior than control animals) when applied before - but not after - the first extinction trial, or when applied before the second extinction trial. The results suggest that environmental treatments such as novelty exposure provide a valuable, nonpharmacological alternative to potentially modulate extinction processes.

  18. Light extinction in the atmosphere

    International Nuclear Information System (INIS)

    Laulainen, N.

    1992-06-01

    Atmospheric aerosol particles originating from natural sources, such as volcanos and sulfur-bearing gas emissions from the oceans, and from human sources, such as sulfur emissions from fossil fuel combustion and biomass burning, strongly affect visual air quality and are suspected to significantly affect radiative climate forcing of the planet. During the daytime, aerosols obscure scenic vistas, while at night they diminish our ability to observe stellar objects. Scattering of light is the main means by which aerosols attenuate and redistribute light in the atmosphere and by which aerosols can alter and reduce visibility and potentially modify the energy balance of the planet. Trends and seasonal variability of atmospheric aerosol loading, such as column-integrated light extinction or optical depth, and how they may affect potential climate change have been difficult to quantify because there have been few observations made of important aerosol optical parameters, such as optical depth, over the globe and over time and often these are of uneven quality. To address questions related to possible climate change, there is a pressing need to acquire more high-quality aerosol optical depth data. Extensive deployment of improved solar radiometers over the next few years will provide higher-quality extinction data over a wider variety of locations worldwide. An often overlooked source of turbidity data, however, is available from astronomical observations, particularly stellar photoelectric photometry observations. With the exception of the Project ASTRA articles published almost 20 years ago, few of these data ever appear in the published literature. This paper will review the current status of atmospheric extinction observations, as highlighted by the ASTRA work and augmented by more recent solar radiometry measurements

  19. Sexual selection protects against extinction.

    Science.gov (United States)

    Lumley, Alyson J; Michalczyk, Łukasz; Kitson, James J N; Spurgin, Lewis G; Morrison, Catriona A; Godwin, Joanne L; Dickinson, Matthew E; Martin, Oliver Y; Emerson, Brent C; Chapman, Tracey; Gage, Matthew J G

    2015-06-25

    Reproduction through sex carries substantial costs, mainly because only half of sexual adults produce offspring. It has been theorized that these costs could be countered if sex allows sexual selection to clear the universal fitness constraint of mutation load. Under sexual selection, competition between (usually) males and mate choice by (usually) females create important intraspecific filters for reproductive success, so that only a subset of males gains paternity. If reproductive success under sexual selection is dependent on individual condition, which is contingent to mutation load, then sexually selected filtering through 'genic capture' could offset the costs of sex because it provides genetic benefits to populations. Here we test this theory experimentally by comparing whether populations with histories of strong versus weak sexual selection purge mutation load and resist extinction differently. After evolving replicate populations of the flour beetle Tribolium castaneum for 6 to 7 years under conditions that differed solely in the strengths of sexual selection, we revealed mutation load using inbreeding. Lineages from populations that had previously experienced strong sexual selection were resilient to extinction and maintained fitness under inbreeding, with some families continuing to survive after 20 generations of sib × sib mating. By contrast, lineages derived from populations that experienced weak or non-existent sexual selection showed rapid fitness declines under inbreeding, and all were extinct after generation 10. Multiple mutations across the genome with individually small effects can be difficult to clear, yet sum to a significant fitness load; our findings reveal that sexual selection reduces this load, improving population viability in the face of genetic stress.

  20. Transport Coefficients of Fluids

    CERN Document Server

    Eu, Byung Chan

    2006-01-01

    Until recently the formal statistical mechanical approach offered no practicable method for computing the transport coefficients of liquids, and so most practitioners had to resort to empirical fitting formulas. This has now changed, as demonstrated in this innovative monograph. The author presents and applies new methods based on statistical mechanics for calculating the transport coefficients of simple and complex liquids over wide ranges of density and temperature. These molecular theories enable the transport coefficients to be calculated in terms of equilibrium thermodynamic properties, and the results are shown to account satisfactorily for experimental observations, including even the non-Newtonian behavior of fluids far from equilibrium.

  1. Comment on the extinct paradox

    International Nuclear Information System (INIS)

    Levine, D.M.

    1983-11-01

    The extinction paradox is a contradiction between geometrical optics results which predict that at high frequencies the scattering cross section of an object should equal its geometrical cross section and rigorous scattering theory which shows that at high frequencies the scattering cross section approaches twice the geometrical cross section of the object. Confusion about the reason for this paradox persists today even though the nature of the paradox was correctly identified many years ago by Brillouin. The resolution of the paradox is restated and illustrated with an example, and then the implications to the interpretation of scattering cross sections are identified

  2. Presidential address: distinction or extinction.

    Science.gov (United States)

    Pressman, Barry D

    2008-10-01

    Despite its continuing scientific successes in imaging, radiology as a specialty is faced with a very difficult and competitive environment. Nonradiologists are more and more interested in vertically integrating imaging into their practices, while teleradiology and picture archiving and communication systems are resulting in the greater isolation of radiologists. Commoditization is a realistic and devastating threat to the survival and professionalism of the specialty. To remain viable as a specialty, radiologists must elevate their practice by subspecializing, becoming more involved with clinical care, and actively interacting with patients and referring clinicians. Distinction will prevent extinction.

  3. Methylphenidate enhances extinction of contextual fear

    OpenAIRE

    Abraham, Antony D.; Cunningham, Christopher L.; Lattal, K. Matthew

    2012-01-01

    Methylphenidate (MPH, Ritalin) is a norepinephrine and dopamine transporter blocker that is widely used in humans for treatment of attention deficit disorder and narcolepsy. Although there is some evidence that targeted microinjections of MPH may enhance fear acquisition, little is known about the effect of MPH on fear extinction. Here, we show that MPH, administered before or immediately following extinction of contextual fear, will enhance extinction retention in C57BL/6 mice. Animals that ...

  4. Are Humans too Numerous to Become Extinct?

    OpenAIRE

    Cairns, John

    2009-01-01

    Some claim that humans are too numerous to become extinct. However, passenger pigeon, once the most numerous birds on the planet, are now extinct. For years, humankind has been damaging its habitat, discharging toxic chemicals into the environment, and having harmful effects on agricultural productivity due to climate change. Humankind s extinction depends on the continuation of various human activities including economic growth, addiction to fossil fuel, over consumption, overpopulation, oc...

  5. The Astronomical Pulse of Global Extinction Events

    Directory of Open Access Journals (Sweden)

    David F.V. Lewis

    2006-01-01

    Full Text Available The linkage between astronomical cycles and the periodicity of mass extinctions is reviewed and discussed. In particular, the apparent 26 million year cycle of global extinctions may be related to the motion of the solar system around the galaxy, especially perpendicular to the galactic plane. The potential relevance of Milankovitch cycles is also explored in the light of current evidence for the possible causes of extinction events over a geological timescale.

  6. Long-term maintenance of immediate or delayed extinction is determined by the extinction-test interval

    OpenAIRE

    Johnson, Justin S.; Escobar, Martha; Kimble, Whitney L.

    2010-01-01

    Short acquisition-extinction intervals (immediate extinction) can lead to either more or less spontaneous recovery than long acquisition-extinction intervals (delayed extinction). Using rat subjects, we observed less spontaneous recovery following immediate than delayed extinction (Experiment 1). However, this was the case only if a relatively long extinction-test interval was used; a relatively short extinction-test interval yielded the opposite result (Experiment 2). Previous data appear co...

  7. An innovative technique to distalize maxillary molar using microimplant supported rapid molar distalizer

    Directory of Open Access Journals (Sweden)

    Meenu Goel

    2013-01-01

    Full Text Available Introduction: In recent years, enhancements in implants have made their use possible as a mode of absolute anchorage in orthodontic patients. In this paper, the authors have introduced an innovative technique to unilaterally distalize the upper left 1 st molar to obtain an ideal Class I molar relationship from a Class II existing molar relationship with an indigenous designed distalizer. Clinical Innovation: For effective unilateral diatalization of molar, a novel cantilever sliding jig assembly was utilized with coil spring supported by a buccally placed single micro implant. The results showed 3 mm of bodily distalization with 1 mm of intrusion and 2° of distal tipping of upper left 1 st molar in 1.5 months. Discussion: This appliance is relatively easy to insert, well-tolerated, and requires minimal patient cooperation compared to other present techniques of molar distalization. Moreover, it is particularly useful in cases that are Class II on one side and Class I on the other, with a minor midline discrepancy and nominal overjet. Patient acceptance level was reported to be within patients physiological and comfort limits.

  8. Intergalactic extinction and the deceleration parameter

    International Nuclear Information System (INIS)

    Meinel, R.

    1981-01-01

    The deceleration parameter q 0 is calculated from the relation between apparent magnitudes m of the brightest galaxies in clusters and their redshifts z considering an intergalactic extinction. The calculation is valid for a Friedman universe, homogeneously filled with dust grains, assuming the extinction to be 0.5 mag at z = 1 and aΛ -1 -law of extinction (according to Oleak and Schmidt 1976). Using the m,z-values of Kristian, Sandage, and Westphal (1978) a formal value of q 0 approximately 2.1 is obtained instead of q 0 approximately 1.6 without consideration of intergalactic extinction. (author)

  9. Interstellar extinction in the Large Magellanic Cloud

    International Nuclear Information System (INIS)

    Nandy, K.; Morgan, D.H.; Willis, A.J.; Wilson, R.; Gondhalekar, P.M.; Houziaux, L.

    1980-01-01

    Recent UV observations together with complementary visible data of several reddened and comparison stars of similar spectral types in the Large Magellanic Cloud have been used to study the interstellar extinction in that galaxy. Most of the reddened stars studied here are located within 2 0 of 30 Doradus and show remarkably high extinction in the far UV, suggesting a large abundance of small particles. From the optical wavelength to 2,600 A the normalised extinction curves of the LMC stars are similar to the mean galactic extinction law. (author)

  10. Mass extinctions vs. uniformitarianism in biological evolution

    Energy Technology Data Exchange (ETDEWEB)

    Bak, P.; Paczuski, M.

    1995-12-31

    It is usually believed that Darwin`s theory leads to a smooth gradual evolution, so that mass extinctions must be caused by external shocks. However, it has recently been argued that mass extinctions arise from the intrinsic dynamics of Darwinian evolution. Species become extinct when swept by intermittent avalanches propagating through the global ecology. These ideas are made concrete through studies of simple mathematical models of co-evolving species. The models exhibit self-organized criticality and describe some general features of the extinction pattern in the fossil record.

  11. Mandibular molar crown-topography, a biological predisposing ...

    African Journals Online (AJOL)

    Mandibular molar crown-topography, a biological predisposing factor to development of caries – a post-mortem analysis of 2500 extracted lower permanent molars at the dental centre, University of Benin teaching hospital.

  12. Prevention of alveolar osteitis after third molar surgery: Comparative ...

    African Journals Online (AJOL)

    Prevention of alveolar osteitis after third molar surgery: Comparative study of the ... for surgical extraction of lower third molar were prospectively, consecutively, and ... Information on demographic, types and level of impaction, indications for ...

  13. Variant Root Morphology of Third Mandibular Molar in Normal and ...

    African Journals Online (AJOL)

    isaac kipyator

    2017-11-12

    Nov 12, 2017 ... ABSTRACT. The mandibular third molar poses a challenge to dental surgeons due to it's unpredictable morphology ... treatment in the School of Dental Sciences since 2010. ... mandibular third molar include presence of three.

  14. The primary extinction and static Debye-Waller factor in the characterization of textured nickel by X-ray diffraction

    International Nuclear Information System (INIS)

    Kryshtab, T.; Palacios G, J.; Cadena A, A.; Kryvko, A.

    2015-01-01

    The texture analysis using X-ray diffraction (XRD) implies measurement of pole figures (Pf) from the diffracted intensities considering the model of kinematical dispersion. The extinction phenomenon results in a decrease of diffracted intensity and that in turn in a decrease of pole densities (Pds). The phenomenon appears in the kinematical theory of XRD as the primary extinction and the secondary extinction to characterize the loss of intensity of kinematical dispersion. In turn, the static Debye-Waller factor is an integral characteristic of defects in crystals that is introduced in the kinematical theory of XRD and also is used in dynamical theory of XRD. In this work the correlation between the primary extinction coefficient and the static Debye-Waller factor in the case of textured nickel was determined. The value of static Debye-Waller factor was determined from the value of the calculated primary extinction coefficient. For the evaluation there were used Pds in the maxima of Pf obtained for 111 and 200 reflections with Mo Kα radiation, and the Pds in the maxima of Pf obtained for the first and second orders of these reflections with Cu Kα and Co Kα radiations. There were calculated the dislocation densities in grains using values of static Debye-Waller factor and the extinction coefficients. The dislocation densities calculated from these two characteristics are practically equal. (Author)

  15. Anatomical physiology of spatial extinction.

    Science.gov (United States)

    Ciçek, Metehan; Gitelman, Darren; Hurley, Robert S E; Nobre, Anna; Mesulam, Marsel

    2007-12-01

    Neurologically intact volunteers participated in a functional magnetic resonance imaging experiment that simulated the unilateral (focal) and bilateral (global) stimulations used to elicit extinction in patients with hemispatial neglect. In peristriate areas, attentional modulations were selectively sensitive to contralaterally directed attention. A higher level of mapping was observed in the intraparietal sulcus (IPS), inferior parietal lobule (IPL), and inferior frontal gyrus (IFG). In these areas, there was no distinction between contralateral and ipsilateral focal attention, and the need to distribute attention globally led to greater activity than either focal condition. These physiological characteristics were symmetrically distributed in the IPS and IFG, suggesting that the effects of unilateral lesions in these 2 areas can be compensated by the contralateral hemisphere. In the IPL, the greater activation by the bilateral attentional mode was seen only in the right hemisphere. Its contralateral counterpart displayed equivalent activations when attention was distributed to the right, to the left, or bilaterally. Within the context of this experiment, the IPL of the right hemisphere emerged as the one area where unilateral lesions can cause the most uncompensated and selective impairment of global attention (without interfering with unilateral attention to either side), giving rise to the phenomenon of extinction.

  16. Biogeography and molar morphology of Pleistocene African elephants: new evidence from Elandsfontein, Western Cape Province, South Africa

    Science.gov (United States)

    Smith, Kathlyn M.; Stynder, Deano D.

    2015-05-01

    Elandsfontein (EFT) is a Middle Pleistocene archaeological/paleontological site located in the Western Cape Province of South Africa. The largest herbivore in the assemblage is Loxodonta atlantica zulu, an extinct member of the genus that includes modern African elephants. No Elephas recki specimens were recovered at EFT, despite their common occurrence in other regions of Africa at the same time. Because E. recki and L. atlantica molars are similar in appearance, but the two species are traditionally viewed as dominating different regions of Africa during the Pleistocene, isolated molars may on occasions have been assessed to species level on the basis of geography rather than morphology. The last morphologic evaluation of EFT elephants was conducted in the 1970s, and revisiting this issue with new specimens provides added insight into the evolution of elephants in Africa. Reevaluating morphological characteristics of EFT elephant molars, through qualitative and quantitative description and comparison with Middle Pleistocene E. recki recki, L. atlantica atlantica, and L. atlantica zulu molar morphology, corroborates assessment of EFT elephants as L. a. zulu. Two recently discovered, previously undescribed molars from EFT show that molars of L. a. zulu exhibit greater variation in enamel thickness, lamellar frequency, and occlusal surface morphology than previously reported. An update of the Pleistocene biogeography of Loxodonta and Elephas indicates that fossil remains of both are often found at the same localities in eastern Africa. Their rare co-occurrences in the north and south, however, suggest geographic separation of the two genera in at least some regions of Africa, which may have been based on habitat preference.

  17. Constraints on Enhanced Extinction Resulting from Extinction Treatment in the Presence of an Added Excitor

    Science.gov (United States)

    Urcelay, Gonzalo P.; Lipatova, Olga; Miller, Ralph R.

    2009-01-01

    Three Pavlovian fear conditioning experiments with rats as subjects explored the effect of extinction in the presence of a concurrent excitor. Our aim was to explore this particular treatment, documented in previous studies to deepen extinction, with novel control groups to shed light on the processes involved in extinction. Relative to subjects…

  18. Timing of extinction relative to acquisition: A parametric analysis of fear extinction in humans

    NARCIS (Netherlands)

    Norrholm, S.D.; Vervliet, B.; Jovanovic, T.; Boshoven, W.; Myers, K.M.; Davis, M.; Rothbaum, B.O.; Duncan, E.J.

    2008-01-01

    Fear extinction is a reduction in conditioned fear following repeated exposure to the feared cue in the absence of any aversive event. Extinguished fear often reappears after extinction through spontaneous recovery. Animal studies suggest that spontaneous recovery can be abolished if extinction

  19. Evidence and mapping of extinction debts for global forest-dwelling reptiles, amphibians and mammals

    Science.gov (United States)

    Chen, Youhua; Peng, Shushi

    2017-03-01

    Evidence of extinction debts for the global distributions of forest-dwelling reptiles, mammals and amphibians was tested and the debt magnitude was estimated and mapped. By using different correlation tests and variable importance analysis, the results showed that spatial richness patterns for the three forest-dwelling terrestrial vertebrate groups had significant and stronger correlations with past forest cover area and other variables in the 1500 s, implying the evidence for extinction debts. Moreover, it was likely that the extinction debts have been partially paid, given that their global richness patterns were also significantly correlated with contemporary forest variables in the 2000 s (but the absolute magnitudes of the correlation coefficients were usually smaller than those calculated for historical forest variables). By utilizing species-area relationships, spatial extinction-debt magnitudes for the three vertebrate groups at the global scale were estimated and the hotspots of extinction debts were identified. These high-debt hotspots were generally situated in areas that did not spatially overlap with hotspots of species richness or high extinction-risk areas based on IUCN threatened status to a large extent. This spatial mismatch pattern suggested that necessary conservation efforts should be directed toward high-debt areas that are still overlooked.

  20. Partial molar volume of mefenamic acid in alcohol at temperatures between T=293.15 and T=313.15 K

    OpenAIRE

    Iqbal, Muhammad J.; Siddiquah, Mahrukh

    2006-01-01

    Apparent molar volume (Vphi), partial molar volume (V), solute-solute interaction parameter (Sv), partial molar expansivity (E(0)2) and isobaric thermal expansion coefficient (alpha2) of mefenamic acid in six different organic solvents namely, methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, and 2-butanol, have been calculated from the measured solution densities over a temperature range of T=293.15 and T=313.15±0.1K. The solution densities were measured by an automated vibrating tube de...

  1. Molar incisor hypomineralization: current research evidences

    Directory of Open Access Journals (Sweden)

    Manikandan Ekambaram

    2016-06-01

    Full Text Available Molar-Incisor Hypomineralization (MIH is a condition of systemic origin that involves one to four first permanent molar teeth and often associated with affected incisors. Although several associations to prenatal/perinatal childhood medical conditions have been reported, the etiology of MIH still remains unclear. The degree of enamel hypomineralization in the affected teeth can vary and the clinical problems associated with the teeth include increased susceptibility to caries, rapid wear, and post-eruptive enamel breakdown. Affected teeth are extremely challenging to treat as the enamel is porous, sensitive and treating clinicians might encounter great difficulty in achieving profound anaesthesia. The first part of thispresentation will give an update on prevalence, potential etiological factors, and management strategies of this condition. The second part of the presentation will cover a systematic review results on bonding strategies to hypomineralized enamel.

  2. [Delayed wound healing post molar extraction].

    Science.gov (United States)

    Schepers, R H; De Visscher, J G A M

    2009-02-01

    One month post extraction of the second left maxillary molar the alveolar extraction site showed no signs of healing and was painful. The patient had been using an oral bisphosphonate during 3 years. Therefore, the lesion was diagnosed as bisphosphonate-induced maxillary osteonecrosis. Treatment was conservative. Since one month later the pain had increased and the wound healing had decreased, a biopsy was carried out. Histopathologic examination revealed a non-Hodgkin lymphoma.

  3. Enamel micromorphology of the tribosphenic molar

    OpenAIRE

    Hanousková, Pavla

    2014-01-01

    The tribosphenic molar is an ancestral type of mammalian teeth and a phy- lotypic stage of the mammalian dental evolution. Yet, in contrast to derived teeth types, its enamel microarchitecture attracted only little attention and the information on that subject is often restricted to statements suggesting a simple homogenous arrangement of a primitive radial prismatic enamel. The present paper tests this prediction with aid of comparative study of eight model species representing the orders Ch...

  4. Incidence of lower second permanent molar impaction.

    Science.gov (United States)

    Evans, R

    1988-08-01

    The incidence of lower second molar impaction was investigated, comparing the records of two samples of 200 orthodontic patients referred consecutively, in 1976 and 1986. A further study compared 50 cases showing both bilateral and unilateral impactions, with a non-impacted control group. This allowed possible causes of the impactions to be examined, particularly concerning the effect of premature loss of deciduous teeth on the distribution of crowding.

  5. Three-dimensional primate molar enamel thickness.

    Science.gov (United States)

    Olejniczak, Anthony J; Tafforeau, Paul; Feeney, Robin N M; Martin, Lawrence B

    2008-02-01

    Molar enamel thickness has played an important role in the taxonomic, phylogenetic, and dietary assessments of fossil primate teeth for nearly 90 years. Despite the frequency with which enamel thickness is discussed in paleoanthropological discourse, methods used to attain information about enamel thickness are destructive and record information from only a single plane of section. Such semidestructive planar methods limit sample sizes and ignore dimensional data that may be culled from the entire length of a tooth. In light of recently developed techniques to investigate enamel thickness in 3D and the frequent use of enamel thickness in dietary and phylogenetic interpretations of living and fossil primates, the study presented here aims to produce and make available to other researchers a database of 3D enamel thickness measurements of primate molars (n=182 molars). The 3D enamel thickness measurements reported here generally agree with 2D studies. Hominoids show a broad range of relative enamel thicknesses, and cercopithecoids have relatively thicker enamel than ceboids, which in turn have relatively thicker enamel than strepsirrhine primates, on average. Past studies performed using 2D sections appear to have accurately diagnosed the 3D relative enamel thickness condition in great apes and humans: Gorilla has the relatively thinnest enamel, Pan has relatively thinner enamel than Pongo, and Homo has the relatively thickest enamel. Although the data set presented here has some taxonomic gaps, it may serve as a useful reference for researchers investigating enamel thickness in fossil taxa and studies of primate gnathic biology.

  6. Extinction of polarized light in ferrofluids with different magnetic particle concentrations

    International Nuclear Information System (INIS)

    Socoliuc, V.; Popescu, L.B.

    2012-01-01

    The magnetic field intensity and nanoparticle concentration dependence of the polarized light extinction in a ferrofluid made of magnetite particles stabilized with technical grade oleic acid dispersed in transformer oil was experimentally investigated. The magnetically induced optical anisotropy, i.e. the dichroism divided by concentration, was found to decrease with increasing sample concentration from 2% to 8%. The magnetically induced change in the optical extinction of light polarized at 54.74 o with respect to the magnetic field direction was found to be positive for the less concentrated sample (2%) and negative for the samples with 4% and 8% magnetic nanoparticle concentrations, the more negative the higher the concentration and field intensity. Based on the theoretically proven fact that the particle orientation mechanism has no effect on the extinction of light polarized at 54.74 o with respect to the field direction, we analyzed the experimental findings in the frames of the agglomeration and long-range pair correlations theories for the magnetically induced optical anisotropy in ferrofluids. We developed a theoretical model in the approximation of single scattering for the optical extinction coefficient of a ferrofluid with magnetically induced particle agglomeration. The model predicts the existence of a polarization independent component of the optical extinction coefficient that is experimentally measurable at 54.74 o polarization angle. The change in the optical extinction of light polarized at 54.74 o is positive if only the formation of straight n-particle chains is considered and may become negative in the hypothesis that the longer chains degenerate to more isotropic structures (polymer-like coils, globules or bundles of chains). The model for the influence on the light absorption of the long-range pair correlations, published elsewhere, predicts that the change in the optical extinction of light polarized at 54.74 o is always negative, the more

  7. Long-Term Maintenance of Immediate or Delayed Extinction Is Determined by the Extinction-Test Interval

    Science.gov (United States)

    Johnson, Justin S.; Escobar, Martha; Kimble, Whitney L.

    2010-01-01

    Short acquisition-extinction intervals (immediate extinction) can lead to either more or less spontaneous recovery than long acquisition-extinction intervals (delayed extinction). Using rat subjects, we observed less spontaneous recovery following immediate than delayed extinction (Experiment 1). However, this was the case only if a relatively…

  8. On the expected relationship between inbreeding, fitness, and extinction

    Directory of Open Access Journals (Sweden)

    Couvet Denis

    2006-06-01

    Full Text Available Abstract We assessed the expected relationship between the level and the cost of inbreeding, measured either in terms of fitness, inbreeding depression or probability of extinction. First, we show that the assumption of frequent, slightly deleterious mutations do agree with observations and experiments, on the contrary to the assumption of few, moderately deleterious mutations. For the same inbreeding coefficient, populations can greatly differ in fitness according to the following: (i population size; larger populations show higher fitness (ii the history of population size; in a population that recovers after a bottleneck, higher inbreeding can lead to higher fitness and (iii population demography; population growth rate and carrying capacity determine the relationship between inbreeding and extinction. With regards to the relationship between inbreeding depression and inbreeding coefficient, the population size that minimizes inbreeding depression depends on the level of inbreeding: inbreeding depression can even decrease when population size increases. It is therefore clear that to infer the costs of inbreeding, one must know both the history of inbreeding (e.g. past bottlenecks and population demography.

  9. Direct correlation of charge transfer absorption with molecular donor:acceptor interfacial area via photothermal deflection spectroscopy

    KAUST Repository

    Domingo, Ester; Vandewal, Koen; Fei, Zhuping; Watkins, Scott E.; Scholes, Fiona H.; Bannock, James H; de Mello, John; Richter, Lee J.; DeLongchamp, Dean M.; Amassian, Aram; Heeney, Martin; Salleo, Alberto; Stingelin, Natalie

    2015-01-01

    . Moreover, we determine the absolute molar extinction coefficient of the CT transition for an archetypical polymer-fullerene interface. The latter is ~100 times lower than the extinction coefficient of the donor chromophore involved, allowing us

  10. Influence of unilateral maxillary first molar extraction treatment on second and third molar inclination in Class II subdivision patients

    NARCIS (Netherlands)

    Livas, Christos; Pandis, Nikolaos; Booij, Johan Willem; Halazonetis, Demetrios J.; Katsaros, Christos; Ren, Yijin

    Objective: To assess the maxillary second molar (M2) and third molar (M3) inclination following orthodontic treatment of Class II subdivision malocclusion with unilateral maxillary first molar (M1) extraction. Materials and Methods: Panoramic radiographs of 21 Class II subdivision adolescents (eight

  11. Can Parallelingualism Save Norwegian from Extinction?

    Science.gov (United States)

    Linn, Andrew R.

    2010-01-01

    Language extinction is one of the most pressing issues in linguistics today, and the literature is full of discussion about how to combat it. Statements that Norwegian is amongst the languages that are already extinct are merely examples of a widespread tendency in the literature towards erroneous information about Norwegian. Nonetheless, there is…

  12. Evaluating herbivore extinction probabilities in Addo Elephant ...

    African Journals Online (AJOL)

    Abstract. Population extinction evaluations, based on the model developed by Dennis et al. (1991) that did not take density dependence into account and that were based on census data, suggest that many of the herbivore species in Addo Elephant National Park (AENP) are vulnerable to local extinction. As a result of low ...

  13. Extinction-Induced Variability in Human Behavior

    Science.gov (United States)

    Kinloch, Jennifer M.; Foster, T. Mary; McEwan, James S. A.

    2009-01-01

    Participants earned points by pressing a computer space bar (Experiment 1) or forming rectangles on the screen with the mouse (Experiment 2) under differential-reinforcement-of-low-rate schedules, followed by extinction. Variability in interresponse time (the contingent dimension) increased during extinction, as for Morgan and Lee (1996);…

  14. Context and Behavioral Processes in Extinction

    Science.gov (United States)

    Bouton, Mark E.

    2004-01-01

    This article provides a selective review and integration of the behavioral literature on Pavlovian extinction. The first part reviews evidence that extinction does not destroy the original learning, but instead generates new learning that is especially context-dependent. The second part examines insights provided by research on several related…

  15. Current extinction rates of reptiles and amphibians.

    Science.gov (United States)

    Alroy, John

    2015-10-20

    There is broad concern that a mass extinction of amphibians and reptiles is now underway. Here I apply an extremely conservative Bayesian method to estimate the number of recent amphibian and squamate extinctions in nine important tropical and subtropical regions. The data stem from a combination of museum collection databases and published site surveys. The method computes an extinction probability for each species by considering its sighting frequency and last sighting date. It infers hardly any extinction when collection dates are randomized and it provides underestimates when artificial extinction events are imposed. The method also appears to be insensitive to trends in sampling; therefore, the counts it provides are absolute minimums. Extinctions or severe population crashes have accumulated steadily since the 1970s and 1980s, and at least 3.1% of frog species have already disappeared. Based on these data and this conservative method, the best estimate of the global grand total is roughly 200 extinctions. Consistent with previous results, frog losses are heavy in Latin America, which has been greatly affected by the pathogenic chytrid fungus Batrachochytrium dendrobatidis. Extinction rates are now four orders-of-magnitude higher than background, and at least another 6.9% of all frog species may be lost within the next century, even if there is no acceleration in the growth of environmental threats.

  16. Interstellar extinction in the Large Magellanic Cloud

    International Nuclear Information System (INIS)

    Nandy, K.; Morgan, D.H.; Willis, A.J.; Wilson, R.; Gondhalekar, P.M.

    1981-01-01

    A systematic investigation of interstellar extinction in the ultraviolet as a function of position in the Large Magellanic Cloud has been made from an enlarged sample of reddened and comparison stars distributed throughout the cloud. Except for one star SK-69-108, the most reddened star of our sample, the shape of the extinction curves for the LMC stars do not show significant variations. All curves show an increase in extinction towards 2200 A, but some have maxima near 2200 A, some near 1900 A. It has been shown that the feature of the extinction curve near 1900 A is caused by the mismatch of the stellar F III 1920 A feature. The strength of this 1920 A feature as a function of luminosity and spectral type has been determined. The extinction curves have been corrected for the mismatch of the 1920 feature and a single mean extinction curve for the LMC normalized to Asub(V) = 0 and Esub(B-V) = 1 is presented. For the same value of Esub(B-V) the LMC stars show the 2200 A feature weaker by a factor 2 as compared with the galactic stars. Higher extinction shortward of 2000 A in the LMC extinction curves than that in our Galaxy, as reported in earlier papers, is confirmed. (author)

  17. Enhancing Divergent Search through Extinction Events

    DEFF Research Database (Denmark)

    Lehman, Joel; Miikkulainen, Risto

    2015-01-01

    for the capacity to evolve. This hypothesis is tested through experiments in two evolutionary robotics domains. The results show that combining extinction events with divergent search increases evolvability, while combining them with convergent search offers no similar benefit. The conclusion is that extinction...

  18. Mass extinctions: Ecological selectivity and primary production

    Science.gov (United States)

    Rhodes, Melissa Clark; Thayer, Charles W.

    1991-09-01

    If mass extinctions were caused by reduced primary productivity, then extinctions should be concentrated among animals with starvation-susceptible feeding modes, active lifestyles, and high-energy budgets. The stratigraphic ranges (by stage) of 424 genera of bivalves and 309 genera of articulate brachiopods suggest that there was an unusual reduction of primary productivity at the Cretaceous/Tertiary (K/T) boundary extinction. For bivalves at the K/T, there were (1) selective extinction of suspension feeders and other susceptible trophic categories relative to deposit feeders and other resistant categories, and (2) among suspension feed-ers, selective extinction of bivalves with active locomotion. During the Permian-Triassic (P/Tr) extinction and Jurassic background time, extinction rates among suspension feeders were greater for articulate brachiopods than for bivalves. But during the K/T event, extinction rates of articulates and suspension-feeding bivalves equalized, possibly because the low-energy budgets of articulates gave them an advantage when food was scarce.

  19. Defining the period of moa extinction

    International Nuclear Information System (INIS)

    Anderson, A.

    2000-01-01

    Few aspects of New Zealand's prehistory have engaged scientific and public attention so consistently as two interlinked questions of moa extinction; when did moas become extinct and why? Answers offered over the last 160 years have run the gamut from chronological antiquity by evolutionary senescence, to within the 19th century Maori and European disturbance. (author)

  20. Immediate extinction promotes the return of fear.

    Science.gov (United States)

    Merz, Christian J; Hamacher-Dang, Tanja C; Wolf, Oliver T

    2016-05-01

    Accumulating evidence indicates that immediate extinction is less effective than delayed extinction in attenuating the return of fear. This line of fear conditioning research impacts the proposed onset of psychological interventions after threatening situations. In the present study, forty healthy men were investigated in a differential fear conditioning paradigm with fear acquisition in context A, extinction in context B, followed by retrieval testing in both contexts 24h later to test fear renewal. Differently coloured lights served as conditioned stimuli (CS): two CS (CS+) were paired with an electrical stimulation that served as unconditioned stimulus, the third CS was never paired (CS-). Extinction took place immediately after fear acquisition or 24h later. One CS+ was extinguished whereas the second CS+ remained unextinguished to control for different time intervals between fear acquisition and retrieval testing. Immediate extinction led to larger skin conductance responses during fear retrieval to both the extinguished and unextinguished CS relative to the CS-, indicating a stronger return of fear compared to delayed extinction. Taken together, immediate extinction is less potent than delayed extinction and is associated with a stronger renewal effect. Thus, the time-point of psychological interventions relative to the offset of threatening situations needs to be carefully considered to prevent relapses. Copyright © 2016 Elsevier Inc. All rights reserved.

  1. Comparison of various state equations for approximation and extrapolation of experimental hydrogen molar volumes in wide temperature and pressure intervals

    International Nuclear Information System (INIS)

    Didyk, A.Yu.; Altynov, V.A.; Wisniewski, R.

    2009-01-01

    The numerical analysis of practically all existing formulae such as expansion series, Tait, logarithm, Van der Waals and virial equations for interpolation of experimental molar volumes versus high pressure was carried out. One can conclude that extrapolating dependences of molar volumes versus pressure and temperature can be valid. It was shown that virial equations can be used for fitting experimental data at relatively low pressures P<3 kbar too in distinction to other equations. Direct solving of a linear equation of the third order relatively to volume using extrapolated virial coefficients allows us to obtain good agreement between existing experimental data for high pressure and calculated values

  2. Mass extinction in poorly known taxa.

    Science.gov (United States)

    Régnier, Claire; Achaz, Guillaume; Lambert, Amaury; Cowie, Robert H; Bouchet, Philippe; Fontaine, Benoît

    2015-06-23

    Since the 1980s, many have suggested we are in the midst of a massive extinction crisis, yet only 799 (0.04%) of the 1.9 million known recent species are recorded as extinct, questioning the reality of the crisis. This low figure is due to the fact that the status of very few invertebrates, which represent the bulk of biodiversity, have been evaluated. Here we show, based on extrapolation from a random sample of land snail species via two independent approaches, that we may already have lost 7% (130,000 extinctions) of the species on Earth. However, this loss is masked by the emphasis on terrestrial vertebrates, the target of most conservation actions. Projections of species extinction rates are controversial because invertebrates are essentially excluded from these scenarios. Invertebrates can and must be assessed if we are to obtain a more realistic picture of the sixth extinction crisis.

  3. Assessing Extinction Risk: Integrating Genetic Information

    Directory of Open Access Journals (Sweden)

    Jason Dunham

    1999-06-01

    Full Text Available Risks of population extinction have been estimated using a variety of methods incorporating information from different spatial and temporal scales. We briefly consider how several broad classes of extinction risk assessments, including population viability analysis, incidence functions, and ranking methods integrate information on different temporal and spatial scales. In many circumstances, data from surveys of neutral genetic variability within, and among, populations can provide information useful for assessing extinction risk. Patterns of genetic variability resulting from past and present ecological and demographic events, can indicate risks of extinction that are otherwise difficult to infer from ecological and demographic analyses alone. We provide examples of how patterns of neutral genetic variability, both within, and among populations, can be used to corroborate and complement extinction risk assessments.

  4. Climate predictors of late quaternary extinctions

    DEFF Research Database (Denmark)

    Nogués-Bravo, David; Ohlemüller, Ralf; Batra, Persaram

    2010-01-01

    Between 50,000 and 3,000 years before present (BP) 65% of mammal genera weighing over 44 kg went extinct, together with a lower proportion of small mammals. Why species went extinct in such large numbers is hotly debated. One of the arguments proposes that climate changes underlie Late Quaternary...... extinctions, but global quantitative evidence for this hypothesis is still lacking. We test the potential role of global climate change on the extinction of mammals during the Late Quaternary. Our results suggest that continents with the highest climate footprint values, in other words, with climate changes...... of greater magnitudes during the Late Quaternary, witnessed more extinctions than continents with lower climate footprint values, with the exception of South America. Our results are consistent across species with different body masses, reinforcing the view that past climate changes contributed to global...

  5. One year Survival Rate of Ketac Molar versus Vitro Molar for Occlusoproximal ART Restorations: a RCT

    Directory of Open Access Journals (Sweden)

    PACHECO Anna Luisa de Brito

    2017-11-01

    Full Text Available Abstract Good survival rates for single-surface Atraumatic Restorative Treatment (ART restorations have been reported, while multi-surface ART restorations have not shown similar results. The aim of this study was to evaluate the survival rate of occluso-proximal ART restorations using two different filling materials: Ketac Molar EasyMix (3M ESPE and Vitro Molar (DFL. A total of 117 primary molars with occluso-proximal caries lesions were selected in 4 to 8 years old children in Barueri city, Brazil. Only one tooth was selected per child. The subjetcs were randomly allocated in two groups according to the filling material. All treatments were performed following the ART premises and all restorations were evaluated after 2, 6 and 12 months. Restoration survival was evaluated using Kaplan-Meier survival analysis and Log-rank test, while Cox regression analysis was used for testing association with clinical factors (α = 5%. There was no difference in survival rate between the materials tested, (HR = 1.60, CI = 0.98–2.62, p = 0.058. The overall survival rate of restorations was 42.74% and the survival rate per group was Ketac Molar = 50,8% and Vitro Molar G2 = 34.5%. Cox regression test showed no association between the analyzed clinical variables and the success of the restorations. After 12 months evaluation, no difference in the survival rate of ART occluso-proximal restorations was found between tested materials.

  6. A phantom extinction? New insights into extinction dynamics of the Don-hare Lepus tanaiticus.

    Science.gov (United States)

    Prost, S; Knapp, M; Flemmig, J; Hufthammer, A K; Kosintsev, P; Stiller, M; Hofreiter, M

    2010-09-01

    The Pleistocene to Holocene transition was accompanied by a worldwide extinction event affecting numerous mammalian species. Several species such as the woolly mammoth and the giant deer survived this extinction wave, only to go extinct a few thousand years later during the Holocene. Another example for such a Holocene extinction is the Don-hare, Lepus tanaiticus, which inhabited the Russian plains during the late glacial. After being slowly replaced by the extant mountain hare (Lepus timidus), it eventually went extinct during the middle Holocene. Here, we report the phylogenetic relationship of L. tanaiticus and L. timidus based on a 339-basepair (bp) fragment of the mitochondrial D-loop. Phylogenetic tree- and network reconstructions do not support L. tanaiticus and L. timidus being different species. Rather, we suggest that the two taxa represent different morphotypes of a single species and the extinction of 'L. tanaiticus' represents the disappearance of a local morphotype rather than the extinction of a species.

  7. Radiologic study of mandibular third molar of Korean youths

    International Nuclear Information System (INIS)

    Ahn, Hyung Kyu

    1982-01-01

    The author has made a study on the classification of the mandibular 3rd molars of Korean youths through dental radiography by means of Pell and Gregory's classification and on the prevalence of the dental caries of distal surface of the mandibular 2nd molar adjacent to the mandibular 3rd molars turned anteriorly. The results are as follow; 1. It was found that the largest case number was class I (272 cases, 52.9%) in the relation of the tooth to the ramus of the mandible and 2nd molar. 2. The mesio-angular position was the largest number (239 cases, 46.5%) in the relation of the long axis of the impacted mandibular 3rd molar to the long axis of the 2nd molar. 3. The mesio-angular position of class I was the largest number (140 cases, 27.2%) in the relation of the tooth to the ramus of the mandible and 2nd molar and the long axis of the impacted mandibular 3rd moral to the long axis of the 2nd molar. 4. The average angle of the long axis of mandibular 3rd molar in mesioangular position or horizontal position to the occlusal plane was 143 W 5. Mandibular 3rd molar with lesion such as dental cries or pericoronitis was 73 cases (14.2). 6. The caries incidence rate of the distal surface of the 2nd molar was about 3.1%.

  8. Development of multiple scattering lidar to retrieve cloud extinction and size information

    International Nuclear Information System (INIS)

    Kim, Dukhyeon; Cheong, Hai Du; Kim, Young Gi; Park, Sun Ho

    2008-01-01

    Traditional Mie scattering cloud lidar have some limitations because of multiple scattering effects. Because this multiple scattering effects induce depolarization of spherical particle and enhancement of extinction coefficient. We cannot measure the phase of water with depolarization lidar, and also cannot measure the extinction coefficient with single FOV(Field Of View)Mie cloud lidar system. In the study, we have developed a multiple field of view Mie cloud liar system which can give many information about the cloud droplet such as cloud effective size, cloud number density, extinction coefficient of cloud, and phase of water through the correction of multiple scattering effects. For this purpose, we have developed a multiple field of view lidar system which composed of 32 different pinholes. Figure 1 shows the schematic diagram and picture of pinholes which start from 100μm to 8mm. Pihole is located at the focal plane of the parabolic mirror, in this case the minimum FOV is 67μrad, maximum FOV is 5.3 mrad. Figure 2 shows Monte Carlo simulation of the multiple scattering photons vs. cloud depth. In this calculation we assumed that wavelength normalized aerosol size(x)is 100, and density of cloud (extinction efficiency)is 0.01m"-1". By measuring FOV dependent signals and aerosol extinction coefficient we can extract effective droplet size through following equations. Here θ"d"is aerosol effective size, and z"j", f, Θ(z)are height, aerosol density dependent function, and angular size of lidar signal at the height z. Finally. f(z)depends on the light mean free path and number of scattering

  9. Trophic redundancy reduces vulnerability to extinction cascades.

    Science.gov (United States)

    Sanders, Dirk; Thébault, Elisa; Kehoe, Rachel; Frank van Veen, F J

    2018-03-06

    Current species extinction rates are at unprecedentedly high levels. While human activities can be the direct cause of some extinctions, it is becoming increasingly clear that species extinctions themselves can be the cause of further extinctions, since species affect each other through the network of ecological interactions among them. There is concern that the simplification of ecosystems, due to the loss of species and ecological interactions, increases their vulnerability to such secondary extinctions. It is predicted that more complex food webs will be less vulnerable to secondary extinctions due to greater trophic redundancy that can buffer against the effects of species loss. Here, we demonstrate in a field experiment with replicated plant-insect communities, that the probability of secondary extinctions is indeed smaller in food webs that include trophic redundancy. Harvesting one species of parasitoid wasp led to secondary extinctions of other, indirectly linked, species at the same trophic level. This effect was markedly stronger in simple communities than for the same species within a more complex food web. We show that this is due to functional redundancy in the more complex food webs and confirm this mechanism with a food web simulation model by highlighting the importance of the presence and strength of trophic links providing redundancy to those links that were lost. Our results demonstrate that biodiversity loss, leading to a reduction in redundant interactions, can increase the vulnerability of ecosystems to secondary extinctions, which, when they occur, can then lead to further simplification and run-away extinction cascades. Copyright © 2018 the Author(s). Published by PNAS.

  10. Bilateral lower second molar impaction in teenagers: An emergent problem?

    Directory of Open Access Journals (Sweden)

    Shinohara Elio

    2010-01-01

    Full Text Available The frequency of simultaneously impacted second and third molars in teenagers is increasing and becoming a common occurrence in adolescent oral surgery practice. The traditional treatment is the removal of the third molar by conventional access but repositioning of the surgical flap to the distal face of the first molar can predispose to complications such as pericoronitis and delayed healing of the attached gingiva. We present a case in which we use the germectomy approach to remove the impacted third molar for the eruption of the second molar through a vestibular incision. This incision offers excellent bone exposure and exit route for the third molar without disturbing the gingiva attached architecture on the distal face of the first molar providing good healing environment.

  11. THE MID-INFRARED EXTINCTION LAW IN THE LARGE MAGELLANIC CLOUD

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Jian; Jiang, B. W.; Xue, M. Y. [Department of Astronomy, Beijing Normal University, Beijing 100875 (China); Li, Aigen, E-mail: jiangao@bnu.edu.cn, E-mail: bjiang@bnu.edu.cn, E-mail: lia@missouri.edu [Department of Physics and Astronomy, University of Missouri, Columbia, MO 65211 (United States)

    2013-10-10

    Based on photometric data from the Spitzer/SAGE survey, using red giants as extinction tracers, the mid-infrared (MIR) extinction laws in the Large Magellanic Cloud (LMC) are derived for the first time in the form of A{sub λ}/A{sub K{sub S}}. This quantity refers to the extinction in the four Infrared Array Camera (IRAC) bands (i.e., [3.6], [4.5], [5.8], and [8.0] μm) relative to the Two Micron All Sky Survey K{sub S} band at 2.16 μm. We obtain the near-infrared extinction coefficient to be E(J – H)/E(H – K{sub S} ) ≈ 1.29 ± 0.04 and E(J – K{sub S} )/E(H – K{sub S} ) ≈ 1.94 ± 0.04. The wavelength dependence of the MIR extinction A{sub λ}/A{sub K{sub S}} in the LMC varies from one sightline to another. The overall mean MIR extinction is A{sub [3.6]}/A{sub K{sub S}}∼0.72±0.03, A{sub [4.5]}/A{sub K{sub S}}∼0.94±0.03, A{sub [5.8]}/A{sub K{sub S}}∼0.58±0.04, and A{sub [8.0]}/A{sub K{sub S}}∼0.62±0.05. Except for the extinction in the IRAC [4.5] μm band, which may be contaminated by the 4.6 μm CO gas absorption of red giants used to trace LMC extinction, the extinction in the other three IRAC bands show a flat curve, close to the Milky Way R{sub V} = 5.5 model extinction curve, where R{sub V} is the optical total-to-selective extinction ratio. The possible systematic bias caused by the correlated uncertainties of K{sub S} – λ and J – K{sub S} is explored in terms of Monte Carlo simulations. We find that this bias could lead to an overestimation of A{sub λ}/A{sub K{sub S}} in the MIR.

  12. THE MID-INFRARED EXTINCTION LAW IN THE LARGE MAGELLANIC CLOUD

    International Nuclear Information System (INIS)

    Gao, Jian; Jiang, B. W.; Xue, M. Y.; Li, Aigen

    2013-01-01

    Based on photometric data from the Spitzer/SAGE survey, using red giants as extinction tracers, the mid-infrared (MIR) extinction laws in the Large Magellanic Cloud (LMC) are derived for the first time in the form of A λ /A K S . This quantity refers to the extinction in the four Infrared Array Camera (IRAC) bands (i.e., [3.6], [4.5], [5.8], and [8.0] μm) relative to the Two Micron All Sky Survey K S band at 2.16 μm. We obtain the near-infrared extinction coefficient to be E(J – H)/E(H – K S ) ≈ 1.29 ± 0.04 and E(J – K S )/E(H – K S ) ≈ 1.94 ± 0.04. The wavelength dependence of the MIR extinction A λ /A K S in the LMC varies from one sightline to another. The overall mean MIR extinction is A [3.6] /A K S ∼0.72±0.03, A [4.5] /A K S ∼0.94±0.03, A [5.8] /A K S ∼0.58±0.04, and A [8.0] /A K S ∼0.62±0.05. Except for the extinction in the IRAC [4.5] μm band, which may be contaminated by the 4.6 μm CO gas absorption of red giants used to trace LMC extinction, the extinction in the other three IRAC bands show a flat curve, close to the Milky Way R V = 5.5 model extinction curve, where R V is the optical total-to-selective extinction ratio. The possible systematic bias caused by the correlated uncertainties of K S – λ and J – K S is explored in terms of Monte Carlo simulations. We find that this bias could lead to an overestimation of A λ /A K S in the MIR

  13. Are Hypomineralized Primary Molars and Canines Associated with Molar-Incisor Hypomineralization?

    Science.gov (United States)

    da Silva Figueiredo Sé, Maria Jose; Ribeiro, Ana Paula Dias; Dos Santos-Pinto, Lourdes Aparecida Martins; de Cassia Loiola Cordeiro, Rita; Cabral, Renata Nunes; Leal, Soraya Coelho

    2017-11-01

    The purpose of this study was to evaluate the prevalence of and relationship between hypomineralized second primary molars (HSPM) and hypomineralized primary canines (HPC) with molar-incisor hypomineralization (MIH) in 1,963 schoolchildren. The European Academy of Paediatric Dentistry (EAPD) criterion was used for scoring HSPM/HPC and MIH. Only children with four permanent first molars and eight incisors were considered in calculating MIH prevalence (n equals 858); for HSPM/HPC prevalence, only children with four primary second molars (n equals 1,590) and four primary canines (n equals 1,442) were considered. To evaluate the relationship between MIH/HSPM, only children meeting both criteria cited were considered (n equals 534), as was true of MIH/HPC (n equals 408) and HSPM/HPC (n equals 360; chi-square test and logistic regression). The prevalence of MIH was 14.69 percent (126 of 858 children). For HSPM and HPC, the prevalence was 6.48 percent (103 of 1,592) and 2.22 percent (32 of 1,442), respectively. A significant relationship was observed between MIH and both HSPM/HPC (PMIH based on HSPM was 6.31 (95 percent confidence interval [CI] equals 2.59 to 15.13) and for HPC was 6.02 (95 percent CI equals 1.08 to 33.05). The results led to the conclusion that both hypomineralized second primary molars and hypomineralized primary canines are associated with molar-incisor hypomineralization, because children with HSPM/HPC are six times more likely to develop MIH.

  14. MANAGEMENT OF MANDIBULAR THIRD MOLAR SURGERY TO PRESERVE PERIODONTAL HEALTH OF SECOND MOLAR

    Directory of Open Access Journals (Sweden)

    Elitsa G. Deliverska

    2017-06-01

    Full Text Available Background: Extraction of impacted third molar violates surrounding soft and bony tissues. Various surgical approaches and surgical technics have an important impact on the periodontal health of the adjacent second molar. Purpose: The aim of this review is to analyse the causes that can affect postoperative periodontal outcomes for the mandibular second molars (LM2 adjacent to the impacted/ semi impacted mandibular third molars (LM3. Material and Methods: Electronic searches were conducted through the MEDLINE (PubMed, Scopus, etc. databases to screen all relevant articles published from inception to April 2017. Results: Different flap techniques had no significant impact on the probing depth reduction or on the clinical attachment level of LM2. Szmyd and paramarginal flap designs may be the most effective in reducing the probing depth after third molar surgery, and the envelope flap may be the least effective. Use of bone substitutes and guided tissue regeneration therapy has been proposed, to eliminate or prevent these periodontal defects, but there is still no consensus on their predictability or clinical benefit. Higher costs and the risk of postoperative inflammatory complications should also be taken into proper account, as with any surgical procedure. “Orthodontic extraction” is indicated for that impacted M3 that present a high risk of postoperative periodontal defects at the distal aspect of adjacent M2. Conclusion: Risk factors associated with bone loss following lower third molar extraction includes age, the direction of the eruption, preoperative bone defects, and resorbtion of the LM2 root surface. Prevention of such periodontal defects continues to challenge clinicians.

  15. Immediate extinction causes a less durable loss of performance than delayed extinction following either fear or appetitive conditioning

    OpenAIRE

    Woods, Amanda M.; Bouton, Mark E.

    2008-01-01

    Five experiments with rat subjects compared the effects of immediate and delayed extinction on the durability of extinction learning. Three experiments examined extinction of fear conditioning (using the conditioned emotional response method), and two experiments examined extinction of appetitive conditioning (using the food-cup entry method). In all experiments, conditioning and extinction were accomplished in single sessions, and retention testing took place 24 h after extinction. In both f...

  16. A rediscussion of the atmospheric extinction and the absolute spectral-energy distribution of Vega

    International Nuclear Information System (INIS)

    Hayes, D.S.; Latham, D.W.

    1975-01-01

    For both the Lick and the Palomar calibrations of the spectral-energy distribution of Vega, the atmospheric extinction was treated incorrectly. We present a model for extinction in the Earth's atmosphere and use this model to calculate corrections to the Lick and Palomar calibrations. We also describe a method that can be used to fabricate mean extinction coefficients for any mountain observatory. We combine selected portions of the corrected Lick and corrected Palomar calibrations with the new Mount Hopkins calibration to generate an absolute spectral-energy distibution of Vega over the wavelength range 3300--10,800 A. Until better measurements become available, we recommend the use of this calibration for all practical applications

  17. Extinction produces context inhibition and multiple-context extinction reduces response recovery in human predictive learning.

    Science.gov (United States)

    Glautier, Steven; Elgueta, Tito; Nelson, James Byron

    2013-12-01

    Two experiments with human participants were used to investigate recovery of an extinguished learned response after a context change using ABC designs. In an ABC design, the context changes over the three successive stages of acquisition (context A), extinction (context B), and test (context C). In both experiments, we found reduced recovery in groups that had extinction in multiple contexts, and that the extinction contexts acquired inhibitory strength. These results confirm those of previous investigations, that multiple-context extinction can produce less response recovery than single-context extinction, and they also provide new evidence for the involvement of contextual inhibitory processes in extinction in humans. The foregoing results are broadly in line with a protection-from-extinction account of response recovery. Yet, despite the fact that we detected contextual inhibition, predictions based on protection-from-extinction were not fully reliable for the single- and multiple-context group differences that we observed in (1) rates of extinction and (2) the strength of context inhibition. Thus, although evidence was obtained for a protection-from-extinction account of response recovery, this account can not explain all of the data.

  18. Maxillary molar distalization with aligners in adult patients: a multicenter retrospective study

    Directory of Open Access Journals (Sweden)

    Serena Ravera

    2016-04-01

    Full Text Available Abstract Background The aim of the present study was to test the hypothesis that bodily maxillary molar distalization was not achievable in aligner orthodontics. Methods Forty lateral cephalograms obtained from 20 non-growing subjects (9 male, 11 female; average age 29.73 years (group S, who underwent bilateral distalization of their maxillary dentition with Invisalign aligners (Align Technology, Inc., San José, CA, USA, were considered for the study. Skeletal class I or class II malocclusion and a bilateral end-to-end class II molar relationship were the main inclusion criteria. Cephalograms were taken at two time points: (T0 pretreatment and (T2 post-treatment. Treatment changes were evaluated between the time points using 39 variables by means of paired t test. The level of significance was set at P < 0.05. Reproducibility of measurements was assessed by the intraclass correlation coefficient (ICC. Results The mean treatment time was 24.3 ± 4.2 months. At the post-treatment point, the first molar moved distally 2.25 mm without significant tipping (P = 0.27 and vertical movements (P = 0.43. The second molar distalization was 2.52 mm without significant tipping (P = 0.056 and vertical movements (P = 0.25. No significant movements were detected on the lower arch. SN^GoGn and SPP^GoGn angles showed no significant differences between pre- and post-treatment cephalograms (P = 0.22 and P = 0.85, respectively. Conclusions Aligner therapy in association with composite attachments and class II elastics can distalize maxillary first molars by 2.25 mm without significant tipping and vertical movements of the crown. No changes to the facial height were revealed.

  19. Mandibular molar with five root canals.

    Science.gov (United States)

    Barletta, Fernando Branco; Dotto, Sidney Ricardo; Reis, Magda de Sousa; Ferreira, Ronise; Travassos, Rosana Maria Coelho

    2008-12-01

    The purpose of this study was to demonstrate the importance of knowledge of the internal anatomy of root canals for the success of endodontic treatment. Lack of knowledge of anatomic variations and their characteristics in different teeth has been pointed out as one of the main causes of endodontic therapy failure. In this report, the authors describe the endodontic treatment of a mandibular first molar with five root canals, evaluate the rate of occurrence of this number of canals, and discuss the importance of their identification and treatment.

  20. Estimating extinction using unsupervised machine learning

    Science.gov (United States)

    Meingast, Stefan; Lombardi, Marco; Alves, João

    2017-05-01

    Dust extinction is the most robust tracer of the gas distribution in the interstellar medium, but measuring extinction is limited by the systematic uncertainties involved in estimating the intrinsic colors to background stars. In this paper we present a new technique, Pnicer, that estimates intrinsic colors and extinction for individual stars using unsupervised machine learning algorithms. This new method aims to be free from any priors with respect to the column density and intrinsic color distribution. It is applicable to any combination of parameters and works in arbitrary numbers of dimensions. Furthermore, it is not restricted to color space. Extinction toward single sources is determined by fitting Gaussian mixture models along the extinction vector to (extinction-free) control field observations. In this way it becomes possible to describe the extinction for observed sources with probability densities, rather than a single value. Pnicer effectively eliminates known biases found in similar methods and outperforms them in cases of deep observational data where the number of background galaxies is significant, or when a large number of parameters is used to break degeneracies in the intrinsic color distributions. This new method remains computationally competitive, making it possible to correctly de-redden millions of sources within a matter of seconds. With the ever-increasing number of large-scale high-sensitivity imaging surveys, Pnicer offers a fast and reliable way to efficiently calculate extinction for arbitrary parameter combinations without prior information on source characteristics. The Pnicer software package also offers access to the well-established Nicer technique in a simple unified interface and is capable of building extinction maps including the Nicest correction for cloud substructure. Pnicer is offered to the community as an open-source software solution and is entirely written in Python.

  1. Root growth during molar eruption in extant great apes.

    Science.gov (United States)

    Kelley, Jay; Dean, Christopher; Ross, Sasha

    2009-01-01

    While there is gradually accumulating knowledge about molar crown formation and the timing of molar eruption in extant great apes, very little is known about root formation during the eruption process. We measured mandibular first and second molar root lengths in extant great ape osteological specimens that died while either the first or second molars were in the process of erupting. For most specimens, teeth were removed so that root lengths could be measured directly. When this was not possible, roots were measured radiographically. We were particularly interested in the variation in the lengths of first molar roots near the point of gingival emergence, so specimens were divided into early, middle and late phases of eruption based on the number of cusps that showed protein staining, with one or two cusps stained equated with immediate post-gingival emergence. For first molars at this stage, Gorilla has the longest roots, followed by Pongo and Pan. Variation in first molar mesial root lengths at this stage in Gorilla and Pan, which comprise the largest samples, is relatively low and represents no more than a few months of growth in both taxa. Knowledge of root length at first molar emergence permits an assessment of the contribution of root growth toward differences between great apes and humans in the age at first molar emergence. Root growth makes up a greater percentage of the time between birth and first molar emergence in humans than it does in any of the great apes. Copyright (c) 2009 S. Karger AG, Basel.

  2. Taking advantage of an unerupted third molar: a case report

    Directory of Open Access Journals (Sweden)

    Igor Figueiredo Pereira

    Full Text Available ABSTRACT Introduction: Treatments with dental surgery seek to displace tooth to the correct position within the dental arch. Objective: To report a clinical case that took advantage of an unerupted third molar. Case history: A male patient, 18 years of age, was referred by his dentist to evaluate the third molars. The clinical exam revealed no visible lower third molars. The computed tomography (CT exam showed the presence of a supernumerary tooth in the region of the mandibular ramus, on the left side, and impaction of the third molar, which was causing root resorption on the second molar, thus making it impossible to remain in the buccal cavity. The preferred option, therefore, was to remove both second molar and the supernumerary tooth, in addition to attaching a device to the third molar during surgery for further traction. Results: After 12 months, the third molar reached the proper position. Conclusion: When a mandibular second permanent molar shows an atypical root resorption, an impacted third molar can effectively substitute the tooth by using an appropriate orthodontic-surgical approach.

  3. Dental computed tomographic imaging as age estimation: morphological analysis of the third molar of a group of Turkish population.

    Science.gov (United States)

    Cantekin, Kenan; Sekerci, Ahmet Ercan; Buyuk, Suleyman Kutalmis

    2013-12-01

    Computed tomography (CT) is capable of providing accurate and measurable 3-dimensional images of the third molar. The aims of this study were to analyze the development of the mandibular third molar and its relation to chronological age and to create new reference data for a group of Turkish participants aged 9 to 25 years on the basis of cone-beam CT images. All data were obtained from the patients' records including medical, social, and dental anamnesis and cone-beam CT images of 752 patients. Linear regression analysis was performed to obtain regression formulas for dental age calculation with chronological age and to determine the coefficient of determination (r) for each sex. Statistical analysis showed a strong correlation between age and third-molar development for the males (r2 = 0.80) and the females (r2 = 0.78). Computed tomographic images are clinically useful for accurate and reliable estimation of dental ages of children and youth.

  4. Amount of fear extinction changes its underlying mechanisms.

    Science.gov (United States)

    An, Bobae; Kim, Jihye; Park, Kyungjoon; Lee, Sukwon; Song, Sukwoon; Choi, Sukwoo

    2017-07-03

    There has been a longstanding debate on whether original fear memory is inhibited or erased after extinction. One possibility that reconciles this uncertainty is that the inhibition and erasure mechanisms are engaged in different phases (early or late) of extinction. In this study, using single-session extinction training and its repetition (multiple-session extinction training), we investigated the inhibition and erasure mechanisms in the prefrontal cortex and amygdala of rats, where neural circuits underlying extinction reside. The inhibition mechanism was prevalent with single-session extinction training but faded when single-session extinction training was repeated. In contrast, the erasure mechanism became prevalent when single-session extinction training was repeated. Moreover, ablating the intercalated neurons of amygdala, which are responsible for maintaining extinction-induced inhibition, was no longer effective in multiple-session extinction training. We propose that the inhibition mechanism operates primarily in the early phase of extinction training, and the erasure mechanism takes over after that.

  5. Attenuation coefficients of soils

    International Nuclear Information System (INIS)

    Martini, E.; Naziry, M.J.

    1989-01-01

    As a prerequisite to the interpretation of gamma-spectrometric in situ measurements of activity concentrations of soil radionuclides the attenuation of 60 to 1332 keV gamma radiation by soil samples varying in water content and density has been investigated. A useful empirical equation could be set up to describe the dependence of the mass attenuation coefficient upon photon energy for soil with a mean water content of 10%, with the results comparing well with data in the literature. The mean density of soil in the GDR was estimated at 1.6 g/cm 3 . This value was used to derive the linear attenuation coefficients, their range of variation being 10%. 7 figs., 5 tabs. (author)

  6. Temporal factors in the extinction of fear in inbred mouse strains differing in extinction efficacy.

    Science.gov (United States)

    MacPherson, Kathryn; Whittle, Nigel; Camp, Marguerite; Gunduz-Cinar, Ozge; Singewald, Nicolas; Holmes, Andrew

    2013-07-05

    Various neuropsychiatric conditions, including posttraumatic stress disorder (PTSD), are characterized by deficient fear extinction, but individuals differ greatly in risk for these. While there is growing evidence that fear extinction is influenced by certain procedural variables, it is unclear how these influences might vary across individuals and subpopulations. To model individual differences in fear extinction, prior studies identified a strain of inbred mouse, 129S1/SvImJ (S1), which exhibits a profound deficit in fear extinction, as compared to other inbred strains, such as C57BL/6J (B6). Here, we assessed the effects of procedural variables on the impaired extinction phenotype of the S1 strain and, by comparison, the extinction-intact B6 strain. The variables studied were 1) the interval between conditioning and extinction, 2) the interval between cues during extinction training, 3) single-cue exposure before extinction training, and 4) extinction of a second-order conditioned cue. Conducting extinction training soon after ('immediately') conditioning attenuated fear retrieval in S1 mice and impaired extinction in B6 mice. Spacing cue presentations with long inter-trial intervals during extinction training augmented fear in S1 and B6 mice. The effect of spacing was lost with one-trial fear conditioning in B6, but not S1 mice. A single exposure to a conditioned cue before extinction training did not alter extinction retrieval, either in B6 or S1 mice. Both the S1 and B6 strains exhibited robust second-order fear conditioning, in which a cue associated with footshock was sufficient to serve as a conditioned exciter to condition a fear association to a second cue. B6 mice extinguished the fear response to the second-order conditioned cue, but S1 mice failed to do so. These data provide further evidence that fear extinction is strongly influenced by multiple procedural variables and is so in a highly strain-dependent manner. This suggests that the efficacy of

  7. Molar Incisor Hypomineralization, Prevalence, and Etiology

    Directory of Open Access Journals (Sweden)

    Sulaiman Mohammed Allazzam

    2014-01-01

    Full Text Available Aim. To evaluate the prevalence and possible etiological factors associated with molar incisor hypomineralization (MIH among a group of children in Jeddah, Saudi Arabia. Methods. A group of 8-12-year-old children were recruited (n=267  from the Pediatric Dental Clinics at the Faculty of Dentistry, King Abdulaziz University. Children had at least one first permanent molar (FPM, erupted or partially erupted. Demographic information, children’s medical history, and pregnancy-related data were obtained. The crowns of the FPM and permanent incisors were examined for demarcated opacities, posteruptive breakdown (PEB, atypical restorations, and extracted FPMs. Children were considered to have MIH if one or more FPM with or without involvement of incisors met the diagnostic criteria. Results. MIH showed a prevalence of 8.6%. Demarcated opacities were the most common form. Maxillary central incisors were more affected than mandibular (P=0.01. The condition was more prevalent in children with history of illnesses during the first four years of life including tonsillitis (P=0.001, adenoiditis (P=0.001, asthma (P=0.001, fever (P=0.014, and antibiotics intake (P=0.001. Conclusions. The prevalence of MIH is significantly associated with childhood illnesses during the first four years of life including asthma, adenoid infections, tonsillitis, fever, and antibiotics intake.

  8. Onset of molar incisor hypomineralization (MIH).

    Science.gov (United States)

    Fagrell, Tobias G; Salmon, Phil; Melin, Lisa; Norén, Jörgen G

    2013-01-01

    The etiological factors and timing of the onset of molar incisor hypomineralization (MIH) are still not clear. The aim of this study was to examine ground radial and sagittal sections from teeth diagnosed with MIH using light microscopy, polarized light microscopy and X-ray micro-computed tomography (XMCT) and to estimate the onset and timing of the MIH and to relate the hypomineralized enamel to the incremental lines. Thirteen extracted permanent first molars diagnosed MIH, were analyzed with light microscopy and XMCT. The hypomineralized areas were mainly located in the mesio-buccal cusps, starting at the enamel-dentin-junction and continuing towards the enamel surface. In a relative gray scale analysis the values decreased from the EDJ towards the enamel surface. The findings indicate that the ameloblasts in the hypomineralized enamel are capable of forming an enamel of normal thickness, but with a substantial reduction of their capacity for maturation of enamel. Chronologically, it is estimated that the timing of the disturbance is at a period during the first 6-7 months of age.

  9. Sealing Occlusal Dentin Caries in Permanent Molars

    DEFF Research Database (Denmark)

    Qvist, Vibeke; Borum, Mette Kit; Møller, Kirsten Dynes

    2017-01-01

    The purpose of this study was to investigate the possibility of postponing restorative intervention of manifest occlusal caries in young, permanent dentition by non-invasive sealing. This RCT-designed study included 521 occlusal lesions in 521 patients aged 6 to 17 y. Based on clinical and radiog......The purpose of this study was to investigate the possibility of postponing restorative intervention of manifest occlusal caries in young, permanent dentition by non-invasive sealing. This RCT-designed study included 521 occlusal lesions in 521 patients aged 6 to 17 y. Based on clinical...... longevity of sealings and restorations until retreatments, and 3) compare effectiveness of sealings and restorations to halt caries progression in sealed lesions and beneath restorations. Furthermore, we aimed to identify factors influencing longevity and the effectiveness of sealings and restorations.......001). The median survival time for sealings not replaced by restorations was 7.3 y (CI, 6.4 y to NA). Survival of sealings was increased in patients with low caries risk and/or excellent oral hygiene, second molars compared with first molars, and lesions not extending the middle one-third of the dentin. Survival...

  10. Hospital autopsy: Endangered or extinct?

    Science.gov (United States)

    Turnbull, Angus; Osborn, Michael; Nicholas, Nick

    2015-08-01

    To determine the hospital autopsy rate for the UK in 2013. A study of data from a 'Freedom of Information' request to all (n=186) acute NHS Trusts within England (n=160), NHS Boards in Scotland (n=14) and Wales (n=7) and Social Care Trusts in Northern Ireland (n=5). Hospital autopsy rates were calculated from the number of hospital autopsies performed in 2013 as a percentage of total inpatient deaths in the Trust that year. The UK response rate was 99% (n=184), yielding a mean autopsy rate of 0.69%. The mean rates were 0.51% (England), 2.13% (Scotland), 0.65% (Wales) and 0.46% (Northern Ireland). 23% (n=38) of all included respondents had a rate of 0% and 86% (n=143) a rate less than 1%. The decline in hospital autopsy has continued relentlessly and, for better or for worse, the practice is on the verge of extinction in the UK. The study highlights to health professionals and policy makers the magnitude of this decline. Further research should investigate the impact of this on patient safety, clinical audit, public health and medical education. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.

  11. Extinction from a rationalist perspective.

    Science.gov (United States)

    Gallistel, C R

    2012-05-01

    The merging of the computational theory of mind and evolutionary thinking leads to a kind of rationalism, in which enduring truths about the world have become implicit in the computations that enable the brain to cope with the experienced world. The dead reckoning computation, for example, is implemented within the brains of animals as one of the mechanisms that enables them to learn where they are (Gallistel, 1990, 1995). It integrates a velocity signal with respect to a time signal. Thus, the manner in which position and velocity relate to one another in the world is reflected in the manner in which signals representing those variables are processed in the brain. I use principles of information theory and Bayesian inference to derive from other simple principles explanations for: (1) the failure of partial reinforcement to increase reinforcements to acquisition; (2) the partial reinforcement extinction effect; (3) spontaneous recovery; (4) renewal; (5) reinstatement; (6) resurgence (aka facilitated reacquisition). Like the principle underlying dead-reckoning, these principles are grounded in analytic considerations. They are the kind of enduring truths about the world that are likely to have shaped the brain's computations. Copyright © 2012 Elsevier B.V. All rights reserved.

  12. Extrações de molares na Ortodontia Molar extractions in orthodontics

    Directory of Open Access Journals (Sweden)

    Marco Antônio Schroeder

    2011-12-01

    Full Text Available O tratamento ortodôntico com extração de molares em pacientes adultos é tecnicamente mais complexo, devido a inúmeros fatores. Em geral, o espaço a ser fechado é maior do que o espaço dos pré-molares e, por isso, a ancoragem é crítica e o tempo de tratamento mais longo. É comum esses casos apresentarem algum grau de comprometimento periodontal por causa da idade dos pacientes e, portanto, necessitam de maior controle da mecânica ortodôntica para reduzir os efeitos colaterais do fechamento do espaço. Por isso, bons resultados de finalização são mais difíceis de ser alcançados. Sendo assim, este artigo tem como objetivo apresentar as razões para a indicação de extração de molares nos tratamentos ortodônticos, as contraindicações, as diferentes fases da mecânica ortodôntica, esclarecer os fatores envolvidos nesse tipo de planejamento e tratamento e apresentar casos clínicos tratados com extração de molares.Orthodontic treatment with extraction of molars in adult patients is technically more complex due to a number of factors. In general, the space to be closed is greater than premolar spaces rendering critical anchorage and longer treatment time. Often such cases exhibit some degree of periodontal involvement due to patient age. Hence, the need for greater control over orthodontic mechanics to reduce the side effects of space closure. Therefore, good finishing results can be more difficult to achieve. Thus, the purpose of this article is to determine the reasons for molar extraction indications, describe different stages of orthodontic mechanics, and explain the issues involved in this kind of planning and treatment. Additionally, it aims at describing some treatments with molar extractions.

  13. Factors affecting root curvature of mandibular first molar

    International Nuclear Information System (INIS)

    Choi, Hang Moon; Yi, Won Jin; Heo, Min Suk; Kim, Jung Hwa; Choi, Soon Chul; Park, Tae Won

    2006-01-01

    To find the cause of root curvature by use of panoramic and lateral cephalometric radiograph. Twenty six 1st graders whose mandibular 1st molars just emerged into the mouth were selected. Panoramic and lateral cephalometric radiograph were taken at grade 1 and 6, longitudinally. In cephalometric radio graph, mandibular plane angle, ramus-occlusal place angle, gonial angle, and gonion-gnathion distance(Go-Gn distance) were measured. In panoramic radiograph, elongated root length and root angle were measured by means of digital subtraction radiography. Occlusal plane-tooth axis angle was measured, too. Pearson correlations were used to evaluate the relationships between root curvature and elongated length and longitudinal variations of all variables. Multiple regression equation using related variables was computed. The pearson correlation coefficient between curved angle and longitudinal variations of occlusal plane-tooth axis angle and ramus-occlusal plane angle was 0.350 and 0.401, respectively (p 1 +0.745X 2 (Y: root angle, X 1 : variation of occlusal plane-tooth axis angle, X 2 : variation of ramus-occlusal plane angle). It was suspected that the reasons of root curvature were change of tooth axis caused by contact with 2nd deciduous tooth and amount of mesial and superior movement related to change of occlusal plane

  14. Autotransplantation of Mandibular Third Molar: A Case Report

    Directory of Open Access Journals (Sweden)

    Pabbati Ravi kumar

    2012-01-01

    Full Text Available Autogenous transplantation is a feasible, fast, and economical option for the treatment of nonsalvageable teeth when a suitable donor tooth is available. This paper presents successful autotransplantation of a mature mandibular left third molar (38 without anatomical variances is used to replace a mandibular left second molar (37. The mandibular second molar was nonrestorable due to extensive root caries and resorption of distal root. After extraction of mandibular second and third molars, root canal therapy was done for the third molar extraorally, and the tooth was reimplanted into the extracted socket of second molar site. After one year, clinical and radiographic examination revealed satisfactory outcome with no signs or symptoms suggestive of pathology. In selected cases, autogenous tooth transplantation, even after complete root formation of the donor tooth, may be considered as a practical treatment alternative to conventional prosthetic rehabilitation or implant treatment.

  15. Function of pretribosphenic and tribosphenic mammalian molars inferred from 3D animation.

    Science.gov (United States)

    Schultz, Julia A; Martin, Thomas

    2014-10-01

    Appearance of the tribosphenic molar in the Late Jurassic (160 Ma) is a crucial innovation for food processing in mammalian evolution. This molar type is characterized by a protocone, a talonid basin and a two-phased chewing cycle, all of which are apomorphic. In this functional study on the teeth of Late Jurassic Dryolestes leiriensis and the living marsupial Monodelphis domestica, we demonstrate that pretribosphenic and tribosphenic molars show fundamental differences of food reduction strategies, representing a shift in dental function during the transition of tribosphenic mammals. By using the Occlusal Fingerprint Analyser (OFA), we simulated the chewing motions of the pretribosphenic Dryolestes that represents an evolutionary precursor condition to such tribosphenic mammals as Monodelphis. Animation of chewing path and detection of collisional contacts between virtual models of teeth suggests that Dryolestes differs from the classical two-phased chewing movement of tribosphenidans, due to the narrowing of the interdental space in cervical (crown-root transition) direction, the inclination angle of the hypoflexid groove, and the unicuspid talonid. The pretribosphenic chewing cycle is equivalent to phase I of the tribosphenic chewing cycle, but the former lacks phase II of the tribosphenic chewing. The new approach can analyze the chewing cycle of the jaw by using polygonal 3D models of tooth surfaces, in a way that is complementary to the electromyography and strain gauge studies of muscle function of living animals. The technique allows alignment and scaling of isolated fossil teeth and utilizes the wear facet orientation and striation of the teeth to reconstruct the chewing path of extinct mammals.

  16. Function of pretribosphenic and tribosphenic mammalian molars inferred from 3D animation

    Science.gov (United States)

    Schultz, Julia A.; Martin, Thomas

    2014-10-01

    Appearance of the tribosphenic molar in the Late Jurassic (160 Ma) is a crucial innovation for food processing in mammalian evolution. This molar type is characterized by a protocone, a talonid basin and a two-phased chewing cycle, all of which are apomorphic. In this functional study on the teeth of Late Jurassic Dryolestes leiriensis and the living marsupial Monodelphis domestica, we demonstrate that pretribosphenic and tribosphenic molars show fundamental differences of food reduction strategies, representing a shift in dental function during the transition of tribosphenic mammals. By using the Occlusal Fingerprint Analyser (OFA), we simulated the chewing motions of the pretribosphenic Dryolestes that represents an evolutionary precursor condition to such tribosphenic mammals as Monodelphis. Animation of chewing path and detection of collisional contacts between virtual models of teeth suggests that Dryolestes differs from the classical two-phased chewing movement of tribosphenidans, due to the narrowing of the interdental space in cervical (crown-root transition) direction, the inclination angle of the hypoflexid groove, and the unicuspid talonid. The pretribosphenic chewing cycle is equivalent to phase I of the tribosphenic chewing cycle, but the former lacks phase II of the tribosphenic chewing. The new approach can analyze the chewing cycle of the jaw by using polygonal 3D models of tooth surfaces, in a way that is complementary to the electromyography and strain gauge studies of muscle function of living animals. The technique allows alignment and scaling of isolated fossil teeth and utilizes the wear facet orientation and striation of the teeth to reconstruct the chewing path of extinct mammals.

  17. Survival of sealants in molars affected by molar-incisor hypomineralization: 18-month follow-up

    Directory of Open Access Journals (Sweden)

    Camila Maria Bullio FRAGELLI

    2017-04-01

    Full Text Available Abstract The objective of this study was to evaluate the clinical survival of sealants applied in first permanent molars (FPMs affected by molar-incisor hypomineralization (MIH, at 18 months of follow-up. Forty-one first permanent molars were selected from 21 children, 6–8 years of age. MIH was classified by one calibrated examiner (kappa = 0.80 according to EAPD criteria. The inclusion criteria were fully erupted FPMs with MIH or sound FPMs (without MIH for which sealant treatment was indicated. The FPMs were assigned to two groups: CG (control group and HG (MIH group. Both groups were treated with sealant (FluroShield. Clinical follow-up was performed from baseline to 18 months to assess anatomical form, marginal adaptation, retention and presence of caries, according to criteria set by the United States Public Health Service-Modified, and was conducted by a blinded examiner (kappa = 0.80. The actuarial method was used to evaluate the survival of the sealants. The survival rates for the groups were compared using Fisher’s exact test (α = 5%. The cumulative survival rates were 81% at 1 month, 68.8% at 6 months, 68.8% at 12 months, and 62.6% at 18 months for CG, and 88% at 1 month, 84% at 6 months, 76% at 12 months, and 72% at 18 months for HG. No significant difference was found between the groups. The sealants in molars affected by MIH presented a survival rate similar to the sealants in the control, suggesting that sealants may be an adequate approach for preventing carious lesions in MIH-affected molars.

  18. New models for age estimation and assessment of their accuracy using developing mandibular third molar teeth in a Thai population.

    Science.gov (United States)

    Duangto, P; Iamaroon, A; Prasitwattanaseree, S; Mahakkanukrauh, P; Janhom, A

    2017-03-01

    Age estimation using developing third molar teeth is considered an important and accurate technique for both clinical and forensic practices. The aims of this study were to establish population-specific reference data, to develop age prediction models using mandibular third molar development, to test the accuracy of the resulting models, and to find the probability of persons being at the age thresholds of legal relevance in a Thai population. A total of 1867 digital panoramic radiographs of Thai individuals aged between 8 and 23 years was selected to assess dental age. The mandibular third molar development was divided into nine stages. The stages were evaluated and each stage was transformed into a development score. Quadratic regression was employed to develop age prediction models. Our results show that males reached mandibular third molar root formation stages earlier than females. The models revealed a high correlation coefficient for both left and right mandibular third molar teeth in both sexes (R = 0.945 and 0.944 in males, R = 0.922 and 0.923 in females, respectively). Furthermore, the accuracy of the resulting models was tested in randomly selected 374 cases and showed low error values between the predicted dental age and the chronological age for both left and right mandibular third molar teeth in both sexes (-0.13 and -0.17 years in males, 0.01 and 0.03 years in females, respectively). In Thai samples, when the mandibular third molar teeth reached stage H, the probability of the person being over 18 years was 100 % in both sexes.

  19. Stress before extinction learning enhances and generalizes extinction memory in a predictive learning task.

    Science.gov (United States)

    Meir Drexler, Shira; Hamacher-Dang, Tanja C; Wolf, Oliver T

    2017-05-01

    In extinction learning, the individual learns that a previously acquired association (e.g. between a threat and its predictor) is no longer valid. This learning is the principle underlying many cognitive-behavioral psychotherapeutic treatments, e.g. 'exposure therapy'. However, extinction is often highly-context dependent, leading to renewal (relapse of extinguished conditioned response following context change). We have previously shown that post-extinction stress leads to a more context-dependent extinction memory in a predictive learning task. Yet as stress prior to learning can impair the integration of contextual cues, here we aim to create a more generalized extinction memory by inducing stress prior to extinction. Forty-nine men and women learned the associations between stimuli and outcomes in a predictive learning task (day 1), extinguished them shortly after an exposure to a stress/control condition (day 2), and were tested for renewal (day 3). No group differences were seen in acquisition and extinction learning, and a renewal effect was present in both groups. However, the groups differed in the strength and context-dependency of the extinction memory. Compared to the control group, the stress group showed an overall reduced recovery of responding to the extinguished stimuli, in particular in the acquisition context. These results, together with our previous findings, demonstrate that the effects of stress exposure on extinction memory depend on its timing. While post-extinction stress makes the memory more context-bound, pre-extinction stress strengthens its consolidation for the acquisition context as well, making it potentially more resistant to relapse. These results have implications for the use of glucocorticoids as extinction-enhancers in exposure therapy. Copyright © 2017 Elsevier Inc. All rights reserved.

  20. Interstellar extinction in the Small Magellanic Cloud

    International Nuclear Information System (INIS)

    Nandy, K.; McLachlan, A.; Thompson, G.I.; Morgan, D.H.; Willis, A.J.; Wilson, R.; Gondhalekar, P.M.; Houziaux, L.

    1982-01-01

    IUE observations of three considerably reddened stars located near the core of the Small Magellanic Cloud and of two comparison stars which are also SMC members are presented. This region contains a considerable amount of dust. The UV spectrum of one of the reddened stars (BBB 338) shows the lambda 2200 feature characteristic of the Galactic extinction curve. This absorption feature is not obvious in the UV spectra of the other two reddened stars. Due to lack of a suitable comparison star it has not been possible to measure the UV extinction of BBB 338. The extinction curves derived for the other two reddened SMC members differ from the mean Galactic law in that they exhibit very weak or absent lambda 2200 and much higher values of far-UV extinction. These differences are greater than have been found for stars in the Large Magellanic Cloud, confirming earlier observations by others. (author)

  1. Anthropogenic stressors and riverine fish extinctions

    NARCIS (Netherlands)

    Dias, M.S.; Tedesco, P.A.; Hugueny, B.; Jézéquel, C.; Beauchard, O.; Brosse, S.; Oberdorff, T.

    2017-01-01

    Human activities are often implicated in the contemporary extinction of contemporary species. Concerningriverine fishes, the major biotic and abiotic threats widely cited include introduction of non-nativespecies, habitat fragmentation and homogenization in stream flow dynamics due to the damming

  2. Are marine and nonmarine extinctions correlated?

    Science.gov (United States)

    Rampino, Michael R.

    Recent papers in Eos have debated the possible relationships between marine mass extinctions, comet showers, and volcanism [Alvarez, 1986; Officer and Grieve, 1986], and ail three might be linked [Rampino, 1987]. Moreover, as Officer and Grieve [ 1986] point out, various other causes have been suggested for given extinction events, including changes in climate, ocean circulation, and sea level fluctuations, possibly related to plate tectonics and continental positions. Also under debate is the issue of whether mass extinctions were gradual, stepped, or geologically sudden events (see, for example, Hut et al. [1987]). A missing ingredient thus far in these debates has been the record of faunal diversity of nonmarine animals. Does this show any agreement with the marine extinction record?

  3. Extinction vulnerability of coral reef fishes.

    Science.gov (United States)

    Graham, Nicholas A J; Chabanet, Pascale; Evans, Richard D; Jennings, Simon; Letourneur, Yves; Aaron Macneil, M; McClanahan, Tim R; Ohman, Marcus C; Polunin, Nicholas V C; Wilson, Shaun K

    2011-04-01

    With rapidly increasing rates of contemporary extinction, predicting extinction vulnerability and identifying how multiple stressors drive non-random species loss have become key challenges in ecology. These assessments are crucial for avoiding the loss of key functional groups that sustain ecosystem processes and services. We developed a novel predictive framework of species extinction vulnerability and applied it to coral reef fishes. Although relatively few coral reef fishes are at risk of global extinction from climate disturbances, a negative convex relationship between fish species locally vulnerable to climate change vs. fisheries exploitation indicates that the entire community is vulnerable on the many reefs where both stressors co-occur. Fishes involved in maintaining key ecosystem functions are more at risk from fishing than climate disturbances. This finding is encouraging as local and regional commitment to fisheries management action can maintain reef ecosystem functions pending progress towards the more complex global problem of stabilizing the climate. © 2011 Blackwell Publishing Ltd/CNRS.

  4. Instrument for long-path spectral extinction measurements in air: application to sizing of airborne particles

    International Nuclear Information System (INIS)

    Paganini, Enrico; Trespidi, Franco; Ferri, Fabio

    2001-01-01

    A novel instrument that is capable of taking spectral extinction measurements over long optical paths (approximately 1-100 m) in the UV, visible, and IR ranges is described. The instrument is fully automated, and the extinction spectrum is acquired in almost real time (approximately 5-10 s) with a resolution of ∼3 nm. Its sensitivity and accuracy were estimated by tests carried out in a clean room that showed that, for optical paths between 50 and 100 m, the extinction coefficient can be detected at levels of ∼10 -5 m -1 . Tests carried out on calibrated latex particles showed that, when it was combined with an appropriate inversion method, the technique could be profitably applied to characterize airborne particulate distributions. By carrying out measurements over optical paths of ∼100 m, the instrument is also capable of detecting extinction coefficients that are due to aerosol concentrations well below the limits imposed by the European Economic Community for atmospheric pollution (150 μg/m3). Scaled over optical paths of ∼10 m, the limit imposed for particle emissions from industrial plants (10 mg/m3) can also be detected sensitively

  5. Unusal canal configuration in maxillary and mandibular second molars

    Directory of Open Access Journals (Sweden)

    Ramachandran Ragunathan

    2016-01-01

    Full Text Available This clinical article describes three different case reports of maxillary and mandibular second molars with the unusual anatomy of single root with a single canal and their endodontic management. An unusual case of bilateralism is observed in the first two cases in the form of single-rooted second mandibular molars in both the quadrant of the same patient. The presence of maxillary second molar with single root and single canal in the third case is unusual.

  6. Interstellar Silicon Depletion and the Ultraviolet Extinction

    Science.gov (United States)

    Mishra, Ajay; Li, Aigen

    2018-01-01

    Spinning small silicate grains were recently invoked to account for the Galactic foreground anomalous microwave emission. These grains, if present, will absorb starlight in the far ultraviolet (UV). There is also renewed interest in attributing the enigmatic 2175 Å interstellar extinction bump to small silicates. To probe the role of silicon in the UV extinction, we explore the relations between the amount of silicon required to be locked up in silicates [Si/H]dust and the 2175 Å bump or the far-UV extinction rise, based on an analysis of the extinction curves along 46 Galactic sightlines for which the gas-phase silicon abundance [Si/H]gas is known. We derive [Si/H]dust either from [Si/H]ISM - [Si/H]gas or from the Kramers- Kronig relation which relates the wavelength-integrated extinction to the total dust volume, where [Si/H]ISM is the interstellar silicon reference abundance and taken to be that of proto-Sun or B stars. We also derive [Si/H]dust from fi�tting the observed extinction curves with a mixture of amorphous silicates and graphitic grains. We fi�nd that in all three cases [Si/H]dust shows no correlation with the 2175 Å bump, while the carbon depletion [C/H]dust tends to correlate with the 2175 Å bump. This supports carbon grains instead of silicates as the possible carrier of the 2175 Å bump. We also �find that neither [Si/H]dust nor [C/H]dust alone correlates with the far-UV extinction, suggesting that the far-UV extinction is a combined effect of small carbon grains and silicates.

  7. Post-Retrieval Extinction Attenuates Cocaine Memories

    OpenAIRE

    Sartor, Gregory C; Aston-Jones, Gary

    2013-01-01

    Recent studies have shown that post-retrieval extinction training attenuates fear and reward-related memories in both humans and rodents. This noninvasive, behavioral approach has the potential to be used in clinical settings to treat maladaptive memories that underlie several psychiatric disorders, including drug addiction. However, few studies to date have used a post-retrieval extinction approach to attenuate addiction-related memories. In the current study, we attempted to disrupt cocaine...

  8. Modelling the extinction of Steller's sea cow

    OpenAIRE

    Turvey, S.T; Risley, C.L

    2005-01-01

    Steller's sea cow, a giant sirenian discovered in 1741 and extinct by 1768, is one of the few megafaunal mammal species to have died out during the historical period. The species is traditionally considered to have been exterminated by ‘blitzkrieg’-style direct overharvesting for food, but it has also been proposed that its extinction resulted from a sea urchin population explosion triggered by extirpation of local sea otter populations that eliminated the shallow-water kelps on which sea cow...

  9. A model for evolution and extinction

    OpenAIRE

    Roberts, Bruce W.; Newman, M. E. J.

    1995-01-01

    We present a model for evolution and extinction in large ecosystems. The model incorporates the effects of interactions between species and the influences of abiotic environmental factors. We study the properties of the model by approximate analytic solution and also by numerical simulation, and use it to make predictions about the distribution of extinctions and species lifetimes that we would expect to see in real ecosystems. It should be possible to test these predictions against the fossi...

  10. Extinction of laminar partially premixed flames

    Energy Technology Data Exchange (ETDEWEB)

    Aggarwal, Suresh K. [Department of Mechanical and Industrial Engineering, University of Illinois at Chicago, 842 W. Taylor Street, Room 2039, MC-251, Chicago, IL 60607-7022 (United States)

    2009-12-15

    Flame extinction represents one of the classical phenomena in combustion science. It is important to a variety of combustion systems in transportation and power generation applications. Flame extinguishment studies are also motivated from the consideration of fire safety and suppression. Such studies have generally considered non-premixed and premixed flames, although fires can often originate in a partially premixed mode, i.e., fuel and oxidizer are partially premixed as they are transported to the reaction zone. Several recent investigations have considered this scenario and focused on the extinction of partially premixed flames (PPFs). Such flames have been described as hybrid flames possessing characteristics of both premixed and non-premixed flames. This paper provides a review of studies dealing with the extinction of PPFs, which represent a broad family of flames, including double, triple (tribrachial), and edge flames. Theoretical, numerical and experimental studies dealing with the extinction of such flames in coflow and counterflow configurations are discussed. Since these flames contain both premixed and non-premixed burning zones, a brief review of the dilution-induced extinction of premixed and non-premixed flames is also provided. For the coflow configuration, processes associated with flame liftoff and blowout are described. Since lifted non-premixed jet flames often contain a partially premixed or an edge-flame structure prior to blowout, the review also considers such flames. While the perspective of this review is broad focusing on the fundamental aspects of flame extinction and blowout, results mostly consider flame extinction caused by the addition of a flame suppressant, with relevance to fire suppression on earth and in space environment. With respect to the latter, the effect of gravity on the extinction of PPFs is discussed. Future research needs are identified. (author)

  11. The Truth About Ballistic Coefficients

    OpenAIRE

    Courtney, Michael; Courtney, Amy

    2007-01-01

    The ballistic coefficient of a bullet describes how it slows in flight due to air resistance. This article presents experimental determinations of ballistic coefficients showing that the majority of bullets tested have their previously published ballistic coefficients exaggerated from 5-25% by the bullet manufacturers. These exaggerated ballistic coefficients lead to inaccurate predictions of long range bullet drop, retained energy and wind drift.

  12. The extinction of the West African lion: whose responsibility?

    NARCIS (Netherlands)

    Nollkaemper, A.

    2014-01-01

    A recently published study showed that the lion in West Africa is now critically endangered and faces extinction. From one angle, this would be just one of the large (though unknown) number of species that has previously faced extinction or has even become extinct. But the risk of extinction of some

  13. Compound Stimulus Extinction Reduces Spontaneous Recovery in Humans

    Science.gov (United States)

    Coelho, Cesar A. O.; Dunsmoor, Joseph E.; Phelps, Elizabeth A.

    2015-01-01

    Fear-related behaviors are prone to relapse following extinction. We tested in humans a compound extinction design ("deepened extinction") shown in animal studies to reduce post-extinction fear recovery. Adult subjects underwent fear conditioning to a visual and an auditory conditioned stimulus (CSA and CSB, respectively) separately…

  14. Caracterizacion de nueve genotipos de maiz (Zea mays L. en relacion a area foliar y coeficiente de extincion de luz Caracterização de nove genótipos de milho (Zea mays L. en relação à área foliar e coeficiente de extinção de luz Evaluation of nine corn (Zea mays L. genotypes in relation to leaf area and light extinction coefficient

    Directory of Open Access Journals (Sweden)

    R.G. Camacho

    1995-08-01

    .A field experiment was carried out to evaluate nine corn genotypes (Arichuna, Baraure, B raquitico, Expe-rimental-2, Foremaiz PB, FM-6, Obregón, Proseca-71 and Tocorón in relation to: mean leaf area per plant, total leaf area per plant (TLA, leaf area index (LAI, grain yield (Y and light extinction coefficient (K at 0.50m, 1.00m, 1.50m, 2.00m and 2.50m of plant height (from soil to flag leaf. Also, correlation and single regression between LAI and yield was performed. Significant genotypical differences for all variables were found, except for mean leaf area per plant Ranging was: mean leaf area per plant (471 cm² for Foremaiz PB and 606 cm² for Baraure; TLA (5,327 cm² for Foremaiz PB and 8,411 for Braquítico; LAI (4.26, Foremaiz PB and 6.67, Braquítico; K (0.23 for Braquítico and 0.42, Arichuna; Y (2, 877, Braquítico and 4,784 kg.ha-1 for Tocoron.The relationship between Y and LAI was not significant (r = 0.07. The relationship of LAI and K was described very well by Beer's law.

  15. AESoP: Astronomical Extinction Spectrophotometer

    Science.gov (United States)

    Linford, Justin; McGraw, J.; Zimmer, P.; Ackermann, M.; Fitch, J.

    2009-01-01

    The Earth's atmosphere is a major obstruction to the precision and accuracy of ground-based photometry. The atmosphere removes light from astronomical objects both by absorption and scattering by constituent molecules, aerosols and clouds. These effects can change significantly over short time periods and over modest angles on the sky. To further understand these effects, the UNM Measurement Astrophysics Group has designed, built and recently deployed the Astronomical Extinction Spectrophotometer (AESoP), a 100mm objective grating spectrometer. By monitoring bright stars in sensibly the same direction as a larger photometric telescope is observing, AESoP will measure the wavelength-dependent extinction due to the Earth's atmosphere from 450nm to 900nm on time scales of approximately one minute. The collocated Astronomical LIDAR for Extinction (ALE) provides a high-precision monochromatic extinction measurement at 527nm. Knowing the extinction at a single wavelength allows us to pin the relative spectra generated by AESoP. These extinction spectra can then be integrated over the bandpass of the photometric telescope system to create real time corrections of observations. We present the design and construction of AESoP along with the preliminary results of our first combined observing campaign. This effort is our first step toward breaking the 1% photometry barrier. This project is funded by AFRL Grant FA9451-04-2-0355

  16. How does climate change cause extinction?

    Science.gov (United States)

    Cahill, Abigail E; Aiello-Lammens, Matthew E; Fisher-Reid, M Caitlin; Hua, Xia; Karanewsky, Caitlin J; Ryu, Hae Yeong; Sbeglia, Gena C; Spagnolo, Fabrizio; Waldron, John B; Warsi, Omar; Wiens, John J

    2013-01-07

    Anthropogenic climate change is predicted to be a major cause of species extinctions in the next 100 years. But what will actually cause these extinctions? For example, will it be limited physiological tolerance to high temperatures, changing biotic interactions or other factors? Here, we systematically review the proximate causes of climate-change related extinctions and their empirical support. We find 136 case studies of climatic impacts that are potentially relevant to this topic. However, only seven identified proximate causes of demonstrated local extinctions due to anthropogenic climate change. Among these seven studies, the proximate causes vary widely. Surprisingly, none show a straightforward relationship between local extinction and limited tolerances to high temperature. Instead, many studies implicate species interactions as an important proximate cause, especially decreases in food availability. We find very similar patterns in studies showing decreases in abundance associated with climate change, and in those studies showing impacts of climatic oscillations. Collectively, these results highlight our disturbingly limited knowledge of this crucial issue but also support the idea that changing species interactions are an important cause of documented population declines and extinctions related to climate change. Finally, we briefly outline general research strategies for identifying these proximate causes in future studies.

  17. [Orthodontic Management of the Impacted Mandibular Second Molar Tooth].

    Science.gov (United States)

    Mah, Michael; Takada, Kenji

    2016-09-01

    When the mandibular permanent second molar becomes impacted, it is identified as a malocclusion that needs treatment as it often leads to unwanted complications such as caries and periodontitis of the adjacent permanent first molar. Other less common complications include root resorption of the adjacent first molar root or continued root development to be in close proximity to the inferior dental alveolar nerve. This paper seeks to differentiate various levels of severity of impaction and review treatment options that are considered clinically available for the proper management of the impacted mandibular permanent second molar. Treatment options that will be discussed in this article include timing of second molar removal for replacement by the third molar, relief of impaction via second premolar removal, surgical repositioning and the combination of third molar removal, surgical exposure and orthodontic uprighting of the impacted tooth. Depending on the severity of the impaction, most impactions can be easily and predictably corrected with nickel titanium archwires or auxillary open coil springs or uprighting springs. Uncommonly, the mandibular permanent second molar can become severely impacted and in close proximity to the inferior dentoalveolar nerve. In these instances, the use of temporary anchorage devices such as microimplants has shown to be successful in uprighting the severely impacted mandibular permanent second molars. © EDP Sciences, SFODF, 2016.

  18. Epidemiological Status of Third Molars in an Iranian Population

    Directory of Open Access Journals (Sweden)

    Mahnaz Sheikhi

    2016-07-01

    Full Text Available Background Impaction of third molars is a common phenomenon. The incidence of impacted third molars varies in different populations. Objectives The aim of this study is to assess radiographic status (root development degree, angulation, and eruption level of the third molar in Iranian population via panoramic radiographs. Patients and Methods 647 patients, ranging in age from 17 - 25, were selected from three regions of Iran. Based on their panoramic radiographs, their root development degree, angulation, and eruption levels were analyzed. Results The angulation of upper third molars were vertical (44.6%, distoangular (44.1%, mesioangular (10.7%, and horizontal (0.6%. For lower third molars, the angulation was mesioangular (44.5%, vertical (33.8%, distoangular (12.2%, and horizontal (9.5%. The eruption levels of maxillary third molars were C > A> B, and for mandibular third molars they were A > B> C. The order of root development prevalence of the maxillary and mandibular third molars was complete > 2/3 > 1/3. Conclusions The most common status of impaction of the third molars in the maxilla was vertical angulation, level C of eruption, and complete root formation. In the mandible it was mesioangular, level A of eruption, and complete root formation. Since the study sample consists of patients from the north, middle, and south of Iran, the sample can represent the whole population of Iran.

  19. Apparent molar volumes and compressibilities of selected electrolytes in dimethylsulfoxide

    International Nuclear Information System (INIS)

    Warminska, Dorota; Grzybkowski, Waclaw

    2010-01-01

    Densities at T = (293.15, 298.15, 303.15, 313.15, 323.15, and 333.15) K and sound velocities at T = 298.15 K of tetraphenylphosphonium bromide, sodium tetraphenylborate, sodium bromide, and sodium perchlorate in dimethylsulfoxide have been measured over the composition range from (0 to 0.3) mol . kg -1 . From these data, apparent molar volumes and apparent molar isentropic compressibilities at infinite dilution as well as the expansibilities have been evaluated. The results have been discussed in terms of employing tetraphenylphosphonium tetraphenylborate as a reference electrolyte in splitting the limiting apparent molar volumes and apparent molar isentropic compressibilities into ionic contributions.

  20. Excess molar volumes and isentropic compressibility of binary systems {trioctylmethylammonium bis(trifluoromethysulfonyl)imide + methanol or ethanol or 1-propanol} at different temperatures

    International Nuclear Information System (INIS)

    Sibiya, P.N.; Deenadayalu, N.

    2008-01-01

    This paper reports measurements of densities for the binary systems of an ionic liquid and an alkanol at T = (298.15, 303.15, and 313.15) K. The IL is trioctylmethylammonium bis(trifluoromethylsulfonyl)imide [OMA] + [Tf 2 N] - and the alkanols are methanol, or ethanol, or 1-propanol. The speed of sound at T = 298.15 K for the same binary systems was also measured. The excess molar volumes and the isentropic compressibilities for the above systems were then calculated from the experimental densities and the speed of sound, respectively. Redlich-Kister smoothing polynomial equation was used to fit the excess molar volume and the deviation in isentropic compressibility data. The partial molar volumes were determined from the Redlich-Kister coefficients. For all the systems studied, the excess molar volumes have both negative and positive values, while the deviations in isentropic compressibility are negative over the entire composition range

  1. Application of the PFV EoS correlation to excess molar volumes of (1-ethyl-3-methylimidazolium ethylsulfate + alkanols) at different temperatures

    International Nuclear Information System (INIS)

    Deenadayalu, N.; Sen, S.; Sibiya, P.N.

    2009-01-01

    The experimental densities for the binary systems of an ionic liquid and an alkanol {1-ethyl-3-methylimidazolium ethylsulfate [EMIM] + [EtSO 4 ] - + methanol or 1-propanol or 2-propanol} were determined at T = (298.15, 303.15, and 313.15) K. The excess molar volumes for the above systems were then calculated from the experimental density values for each temperature. The Redlich-Kister smoothing polynomial was used to fit the experimental results and the partial molar volumes were determined from the Redlich-Kister coefficients. For all the systems studied, the excess molar volume results were negative over the entire composition range for all the temperatures. The excess molar volumes were correlated with the pentic four parameter virial (PFV) equation of state (EoS) model

  2. Extinction rates in North American freshwater fishes, 1900-2010

    Science.gov (United States)

    Burkhead, Noel M.

    2012-01-01

    Widespread evidence shows that the modern rates of extinction in many plants and animals exceed background rates in the fossil record. In the present article, I investigate this issue with regard to North American freshwater fishes. From 1898 to 2006, 57 taxa became extinct, and three distinct populations were extirpated from the continent. Since 1989, the numbers of extinct North American fishes have increased by 25%. From the end of the nineteenth century to the present, modern extinctions varied by decade but significantly increased after 1950 (post-1950s mean = 7.5 extinct taxa per decade). In the twentieth century, freshwater fishes had the highest extinction rate worldwide among vertebrates. The modern extinction rate for North American freshwater fishes is conservatively estimated to be 877 times greater than the background extinction rate for freshwater fishes (one extinction every 3 million years). Reasonable estimates project that future increases in extinctions will range from 53 to 86 species by 2050.

  3. An Investigation into the Effect of Hydrodynamic Cavitation on Diesel using Optical Extinction

    Science.gov (United States)

    Lockett, R. D.; Fatmi, Z.; Kuti, O.; Price, R.

    2015-12-01

    A conventional diesel and paraffinic-rich model diesel fuel were subjected to sustained cavitation in a custom-built high-pressure recirculation flow rig. Changes to the spectral extinction coefficient at 405 nm were measured using a simple optical arrangement. The spectral extinction coefficient at 405 nm for the conventional diesel sample was observed to increase to a maximum value and then asymptotically decrease to a steady-state value, while that for the paraffinic-rich model diesel was observed to progressively decrease. It is suggested that this is caused by the sonochemical pyrolysis of mono-aromatics to form primary soot-like carbonaceous particles, which then coagulate to form larger particles, which are then trapped by the filter, leading to a steady-state spectral absorbance.

  4. The Late Ordovician Extinction: How it became the best understood of the five major extinctions.

    Science.gov (United States)

    Sheehan, P.

    2003-04-01

    The end Ordovician extinction has become arguably the best-understood major extinction event in Earth History. A plethora of workers have established the pattern of faunal change and causes of the extinction with remarkably little disagreement. The first indication of increased extinction at the end of the Ordovician was a graph of global diversity patterns by Norman Newell in 1967, although he did not recognize it as a major event. The presence of a major extinction event became clear as William Berry and Art Boucot assembled data for Silurian correlation charts in the late 1960s. The first reports of North African glaciation in the late 1960s provided a cause for the extinction and study of the event snowballed. It was no accident that recognition of the extinction began in North America, because it was there that the extinction completely overturned faunas in the epicontinental seas. Glacio-eustatic regression of shallow seaway coincided with the disappearance of endemic Laurentian faunas and replacement by a highly cosmopolitan fauna in the Silurian. Once the event was established in North America, paleontologists soon found evidence of the event around the globe. The well-documented Hirnantia Fauna was found to correspond to the glacial interval, and Pat Brenchley soon recognized that there were two pulses of extinction, at the beginning and end of the glaciation. At the same time that the faunal changes were being documented geologic studies of the glaciation provided information on the environmental changes associated with the extinction. The timing of the glacial maximum was established in Africa and by the presence of dropstones in high latitude marine rocks. The 1990s saw geochemical techniques employed that allowed examination of atmospheric CO2 and temperature changes. In many places carbonate deposition declined. Glacio-eustatic regression was obvious in many areas, and a sea-level decline in the range of 50-100 m was established. Shallow

  5. Immediate Extinction Causes a Less Durable Loss of Performance than Delayed Extinction following Either Fear or Appetitive Conditioning

    Science.gov (United States)

    Woods, Amanda M.; Bouton, Mark E.

    2008-01-01

    Five experiments with rat subjects compared the effects of immediate and delayed extinction on the durability of extinction learning. Three experiments examined extinction of fear conditioning (using the conditioned emotional response method), and two experiments examined extinction of appetitive conditioning (using the food-cup entry method). In…

  6. Bilateral Alternating Auditory Stimulations Facilitate Fear Extinction and Retrieval

    OpenAIRE

    Boukezzi, Sarah; Silva, Catarina; Nazarian, Bruno; Rousseau, Pierre-François; Guedj, Eric; Valenzuela-Moguillansky, Camila; Khalfa, Stéphanie

    2017-01-01

    Disruption of fear conditioning, its extinction and its retrieval are at the core of posttraumatic stress disorder (PTSD). Such deficits, especially fear extinction delay, disappear after alternating bilateral stimulations (BLS) during eye movement desensitization and reprocessing (EMDR) therapy. An animal model of fear recovery, based on auditory cued fear conditioning and extinction learning, recently showed that BLS facilitate fear extinction and fear extinction retrieval. Our goal was to ...

  7. Evaluation of telemedicine systems for impacted third molars diagnosis

    Directory of Open Access Journals (Sweden)

    Duka Miloš

    2009-01-01

    Full Text Available Background/Aim. In the last twenty years significant advances have been made in the fields of information and telecommunication technology in health care applications, with a positive impact on the health care practice. The need for remote diagnosis and planning of interventions is of special importance in military health care, and health management of immobile persons, and those with special needs. In cases such as these, availability of specialist health care is mainly limited by geographic and financial factors. The aim of this study was to investigate practical usability of telemedicine approaches in everyday management of oral surgery patients in terms of reliability of established diagnosis and indications for oral surgery treatment of the third molars. Methods. Our experimental randomized study enrolled 432 randomly selected patients of both genders, aged 20 to 87 years, undergoing panoramic radiography for some reason in the Centre for Dental Radiography in Belgrade. In addition to radiography, photographs of the face and mouth cavity were taken. These images were uploaded to the web server specially dedicated to the study purposes, and then transmitted to teledentists, i.e. oral surgeons, who made remote diagnoses. Diagnostic agreement was determined by way of the Cohen's kappa coefficient, and diagnostic sensitivity (SE, specificity (SP, and effectiveness (EFF were also established. Statistical significance was determined and comparisons performed by using the z-test, and testing of non-parametric characteristics by using the McNemar's χ2 test for p = 0.05 significance cut-off. Results. The results obtained by analyzed images and diagnostic assessment of the clinical diagnosis (kappa = 0.99, SE = 99%, SP = 99%, EFF = 99%, for 95% CI indicate an almost complete diagnostic agreement. The differences in diagnosis were not statistically significant. Conclusion. Diagnostic assessment of the clinical diagnosis of impacted or semi

  8. Ceramic onlay for endodontically treated mandibular molar

    Directory of Open Access Journals (Sweden)

    Roopadevi Garlapati

    2014-01-01

    Full Text Available Restoration of endodontically treated teeth is important for the success of endodontic treatment. In full coverage restorations, maximum amount of tooth structure is compromised, so as to conserve the amount of tooth structure partial coverage restorations, can be preferred. This case report is on fabrication of a conservative tooth colored restoration for an endodontically treated posterior tooth. A 22-year-old male patient presented with pain in the mandibular left first molar. After endodontic treatment, composite material was used as postendodontic restoration. The tooth was then prepared to receive a ceramic onlay and bonded with self-adhesive universal resin cement. Ceramic onlay restoration was periodically examined up to 2 years.

  9. Presence of third molars in orthodontic patients from northern Greece

    Directory of Open Access Journals (Sweden)

    Barka G

    2012-05-01

    Full Text Available Georgia Barka,1 Georgios Tretiakov,1 Theodosios Theodosiou,2 Ioulia Ioannidou-Marathiotou31School of Dentistry, 2Biostatistics, Department of Informatics, School of Natural Sciences, 3Department of Orthodontics, School of Dentistry, Aristotle University of Thessaloniki, Thessaloniki, GreeceObjective: The purpose of the present study was to investigate the frequency of presence of third molar teeth and their distribution in each jaw and each side, according to sex, in a group of orthodontic patients with permanent dentition from northern Greece.Methods: The sample included panoramic radiographs from 220 patients with permanent dentition (mean age 13.62 ± 1.81. The Χ2 test was used to assess the relationships between the variables, and the Fisher's exact test was used in cases where the expected frequencies in each cell were <5.Results: The frequency of third molar presence was 79.1%, and 20.9% was the frequency of third molar agenesis. Intersexual differences in the number of third molars was not statistically significant. There was a correlation between the distribution of third molars on the right and the left side (Fisher's exact test = 100.788; P = 0. The two sides showed the same tendency toward the presence or absence of third molars. A correlation was also found between the distribution of maxillary and mandibular third molars (Fisher's exact test = 24.372; P = 0. In each jaw, the presence or absence of third molars was highly related to the number of third molars found in the other jaw.Conclusion: The present results showed that in this orthodontic group of northern Greek patients, presence accounted for 79.1% and agenesis for 20.9%. No significant difference was found between the frequencies of third molar presence on the left and right sides in either the maxilla or mandible.Keywords: third molars, presence, orthodontic population, Greeks

  10. Extinction Generates Outcome-Specific Conditioned Inhibition.

    Science.gov (United States)

    Laurent, Vincent; Chieng, Billy; Balleine, Bernard W

    2016-12-05

    Extinction involves altering a previously established predictive relationship between a cue and its outcome by repeatedly presenting that cue alone. Although it is widely accepted that extinction generates some form of inhibitory learning [1-4], direct evidence for this claim has been lacking, and the nature of the associative changes induced by extinction have, therefore, remained a matter of debate [5-8]. In the current experiments, we used a novel behavioral approach that we recently developed and that provides a direct measure of conditioned inhibition [9] to compare the influence of extinguished and non-extinguished cues on choice between goal-directed actions. Using this approach, we provide direct evidence that extinction generates outcome-specific conditioned inhibition. Furthermore, we demonstrate that this inhibitory learning is controlled by the infralimbic cortex (IL); inactivation of the IL using M4 DREADDs abolished outcome-specific inhibition and rendered the cue excitatory. Importantly, we found that context modulated this inhibition. Outside its extinction context, the cue was excitatory and functioned as a specific predictor of its previously associated outcome, biasing choice toward actions earning the same outcome. In its extinction context, however, the cue acted as a specific inhibitor and biased choice toward actions earning different outcomes. Context modulation of these excitatory and inhibitory memories was mediated by the dorsal hippocampus (HPC), suggesting that the HPC and IL act in concert to control the influence of conditioned inhibitors on choice. These findings demonstrate for the first time that extinction turns a cue into a net inhibitor that can influence choice via counterfactual action-outcome associations. Copyright © 2016 Elsevier Ltd. All rights reserved.

  11. Elevational distribution and extinction risk in birds.

    Directory of Open Access Journals (Sweden)

    Rachel L White

    Full Text Available Mountainous regions are hotspots of terrestrial biodiversity. Unlike islands, which have been the focus of extensive research on extinction dynamics, fewer studies have examined mountain ranges even though they face increasing threats from human pressures - notably habitat conversion and climate change. Limits to the taxonomic and geographical extent and resolution of previously available information have precluded an explicit assessment of the relative role of elevational distribution in determining extinction risk. We use a new global species-level avian database to quantify the influence of elevational distribution (range, maximum and midpoint on extinction risk in birds at the global scale. We also tested this relationship within biogeographic realms, higher taxonomic levels, and across phylogenetic contrasts. Potential confounding variables (i.e. phylogenetic, distributional, morphological, life history and niche breadth were also tested and controlled for. We show that the three measures of elevational distribution are strong negative predictors of avian extinction risk, with elevational range comparable and complementary to that of geographical range size. Extinction risk was also found to be positively associated with body weight, development and adult survival, but negatively associated with reproduction and niche breadth. The robust and consistent findings from this study demonstrate the importance of elevational distribution as a key driver of variation in extinction dynamics in birds. Our results also highlight elevational distribution as a missing criterion in current schemes for quantifying extinction risk and setting species conservation priorities in birds. Further research is recommended to test for generality across non-avian taxa, which will require an advance in our knowledge of species' current elevational ranges and increased efforts to digitise and centralise such data.

  12. Measurements of stratospheric Pinatubo aerosol extinction profiles by a Raman lidar

    International Nuclear Information System (INIS)

    Abo, Makoto; Nagasawa, Chikao.

    1992-01-01

    The Raman lidar has been used for remote measurements of water vapor, ozone and atmospheric temperature in the lower troposphere because the Raman cross section is three orders smaller than the Rayleigh cross section. The authors estimated the extinction coefficients of the Pinatubo volcanic aerosol in the stratosphere using a Raman lidar. If the precise aerosol extinction coefficients are derived, the backscatter coefficient of a Mie scattering lidar will be more accurately estimated. The Raman lidar has performed to measure density profiles of some species using Raman scattering. Here the authors used a frequency-doubled Nd:YAG laser for transmitter and received nitrogen vibrational Q-branch Raman scattering signal. Ansmann et al. (1990) derived tropospherical aerosol extinction profiles with a Raman lidar. The authors think that this method can apply to dense stratospheric aerosols such as Pinatubo volcanic aerosols. As dense aerosols are now accumulated in the stratosphere by Pinatubo volcanic eruption, the error of Ramen lidar signal regarding the fluctuation of air density can be ignored

  13. Microleakage of different adhesive systems in primary molars ...

    African Journals Online (AJOL)

    Background and aim: This study aimed to examine the microleakage of class V cavities of primary molars prepared by either a conventional dental bur or Er:YAG laser and one of two different adhesive systems. Methods: A total of 50 tooth samples from primary molars were used in this study. They were randomly assigned ...

  14. Changes in heart rate during third molar surgery

    NARCIS (Netherlands)

    Hollander, M. H. J.; Schortinghuis, J.; Vissink, A.

    2016-01-01

    Anxiety is an undesirable psychological phenomenon. Patients are usually anxious when subjected to third molar surgery, but the pattern of anxiety is unknown. The aim of this study was to assess the intensity and course of anxiety during third molar surgery. This study included 48 consecutive

  15. Taurodont molars: Review of literature and radiological features

    International Nuclear Information System (INIS)

    Saini, T.; Wilson, C. A.

    1990-01-01

    Taurodontic molar teeth are present as a clinical entity in modem man. This is a suggestion that the occurrence has a racial bias. The importance of the differential diagnosis of teeth with enlarged pulp is discussed, and the possible influence of taurodontic molars on treatment planning is outlined. (author)

  16. Management of inflammatory complications in third molar surgery: A ...

    African Journals Online (AJOL)

    Background: Pain, swelling and trismus are common complications associated with third molar surgery. These complications have been reported to have an adverse effect on the quality of life of patients undergoing third molar surgery. Objective: To review the different modalities of minimizing inflammatory complications in ...

  17. Excess molar volumes and isentropic compressibilities of binary

    Indian Academy of Sciences (India)

    Excess molar volumes (E) and deviation in isentropic compressibilities (s) have been investigated from the density and speed of sound measurements of six binary liquid mixtures containing -alkanes over the entire range of composition at 298.15 K. Excess molar volume exhibits inversion in sign in one binary ...

  18. Molar incisor hypomineralisation: clinical management of the young patient.

    LENUS (Irish Health Repository)

    Daly, Dympna

    2009-04-01

    Molar incisor hypomineralisation (MIH) is a common developmental condition resulting in enamel defects in first permanent molars and permanent incisors. It presents at eruption of these teeth. Early diagnosis is essential since rapid breakdown of tooth structure may occur, giving rise to acute symptoms and complicated treatment. The purpose of this article is to review MIH and illustrate its clinical management in young children.

  19. Fatigue resistance of CAD/CAM resin composite molar crowns.

    NARCIS (Netherlands)

    Shembish, F.A.; Tong, H.; Kaizer, M.; Janal, M.N.; Thompson, V.P.; Opdam, N.J.M.; Zhang, Y.

    2016-01-01

    OBJECTIVE: To demonstrate the fatigue behavior of CAD/CAM resin composite molar crowns using a mouth-motion step-stress fatigue test. Monolithic leucite-reinforced glass-ceramic crowns were used as a reference. METHODS: Fully anatomically shaped monolithic resin composite molar crowns (Lava

  20. Variant root morphology of third mandibular molar in normal and ...

    African Journals Online (AJOL)

    The mandibular third molar poses a challenge to dental surgeons due to it's unpredictable morphology which leads to increased difficulty during its extraction. The root morphology of the third molar is considered to be the most variable in the human dentition. The study aims to document these variations which will be useful ...

  1. Extinctions. Paleontological baselines for evaluating extinction risk in the modern oceans.

    Science.gov (United States)

    Finnegan, Seth; Anderson, Sean C; Harnik, Paul G; Simpson, Carl; Tittensor, Derek P; Byrnes, Jarrett E; Finkel, Zoe V; Lindberg, David R; Liow, Lee Hsiang; Lockwood, Rowan; Lotze, Heike K; McClain, Craig R; McGuire, Jenny L; O'Dea, Aaron; Pandolfi, John M

    2015-05-01

    Marine taxa are threatened by anthropogenic impacts, but knowledge of their extinction vulnerabilities is limited. The fossil record provides rich information on past extinctions that can help predict biotic responses. We show that over 23 million years, taxonomic membership and geographic range size consistently explain a large proportion of extinction risk variation in six major taxonomic groups. We assess intrinsic risk-extinction risk predicted by paleontologically calibrated models-for modern genera in these groups. Mapping the geographic distribution of these genera identifies coastal biogeographic provinces where fauna with high intrinsic risk are strongly affected by human activity or climate change. Such regions are disproportionately in the tropics, raising the possibility that these ecosystems may be particularly vulnerable to future extinctions. Intrinsic risk provides a prehuman baseline for considering current threats to marine biodiversity. Copyright © 2015, American Association for the Advancement of Science.

  2. Prevalent of root resorption of second molar adjustment the impacted third molar in prepiacal and panoramic radiographs

    Directory of Open Access Journals (Sweden)

    Mohammad Ebrahimi Saravi

    2013-10-01

    Full Text Available   Background and Aims: Impacted third molar reduces the bone level in the distal aspect of second molar, and sometimes it can lead to root resorption of the adjacent tooth. The purpose of this study was to determine this resorption using panoramic and periapical radiographs.   Materials and Methods: In this cross-sectional descriptive study 54 patient (28 men, 26 women above 15 years old with the average of 22 years in Oral and Maxillofacial Department of Tehran University were studied. A periapical radiography from the third molar and a panoramic radiograph were taken from each patient (Because of their routine use and evaluation of accuracy of panoramic compared with periapical, and the magnitude of the root resorption for the second molar was determined by 2 observers and written in a questionnaire. Data were analyzed using Fisher test.   Results: The prevalence of the root resorption of the second molar adjacent to the impacted third molar in the panoramic and the periapical radiographies, with respect to the limitation of the sample size were 46.3% and 31.5%, respectively, with 95% confidence(P>0.05. Most of these resorptions were in the cervical third of the second molar roots and in cases in which the third molars were mesially oriented or horizontal. There was also no significant difference between panoramic and periapical radiographs.   Conclusion: Due to the increased risk of the resorption of the second molar adjacent to the third molar, extraction of the impacted third molars, especiall y mesially oriented or horizontal ones are recommended.

  3. Facilitation of extinction and re-extinction of operant behavior in mice by chlordiazepoxide and D-cycloserine.

    Science.gov (United States)

    Leslie, Julian C; Norwood, Kelly

    2013-05-01

    The aim was to compare operant extinction with re-extinction following re-acquisition and to investigate neuropharmacological mechanisms through administration of drugs potentiating GABAergic or glutamatergic systems. Groups of C57Bl/6 mice were trained to lever press for food on a fixed ratio schedule, then extinguished with or without pre-session chlordiazepoxide or post-session d-cycloserine administration (15mg/kg in each case), then retrained to lever press for food, then re-extinguished with or without pre-session chlordiazepoxide or post-session d-cycloserine. Under vehicle injections, extinction and re-extinction curves were indistinguishable, but drug treatments showed that there was less resistance to extinction in the re-extinction phase. Chlordiazepoxide facilitated extinction and re-extinction, with an earlier effect during re-extinction. d-Cycloserine also facilitated extinction and re-extinction, with some evidence of an earlier effect during re-extinction. These results replicate and extend earlier findings with operant extinction, but differ from some previous reports of d-cycloserine on re-extinction of Pavlovian conditioned fear. Implications for accounts of the similarities and differences between neural mechanisms of extinction following either Pavlovian or operant conditioning, and applications of these findings, are discussed. Copyright © 2013 Elsevier Inc. All rights reserved.

  4. Impacted third molar transplantation on the malpracticed extraction socket.

    Science.gov (United States)

    Kim, Soung Min; Amponsah, Emmanuel K

    2017-12-01

    Autotransplantation with or without endodontic therapy is regarded as an alternative treatment option for the replacement of missing teeth. A primary responsibility of a maxillofacial surgeon is to reverse any malpractice to promote successful outcomes and improve the patient's quality of life. This paper presents a malpractice case of incorrect extraction of the lower second molar instead of the impacted third molar. A simple technique of transplanting the impacted third molar to the site of the extracted second molar is introduced by a maxillofacial specialist in Ghana. By making an intentional root socket and fixation without using additional appliances, a novel second molar was achieved with complete recovery. This patient was followed after transplant for a four-year period with the best satisfaction. A grant of the Korean Health Technology R&D Project, Ministry of Health & Welfare, Republic of Korea. (HI15C0689).

  5. PULPOTOMIES WITH PORTLAND CEMENT IN HUMAN PRIMARY MOLARS

    Science.gov (United States)

    Conti, Taísa Regina; Sakai, Vivien Thiemy; Fornetti, Ana Paula Camolese; Moretti, Ana Beatriz Silveira; Oliveira, Thais Marchini; Lourenço, Natalino; Machado, Maria Aparecida Andrade Moreira; Abdo, Ruy Cesar Camargo

    2009-01-01

    Two clinical cases in which Portland cement (PC) was applied as a medicament after pulpotomy of mandibular primary molars in children are presented. Pulpotomy using PC was carried out in two mandibular first molars and one mandibular second molar, which were further followed-up. At the 3, 6 and 12-month follow-up appointments, clinical and radiographic examinations of the pulpotomized teeth and their periradicular area revealed that the treatments were successful in maintaining the teeth asymptomatic and preserving pulpal vitality. Additionally, the formation of a dentin bridge immediately below the PC could be observed in the three molars treated. PC may be considered as an effective alternative for primary molar pulpotomies, at least in a short-term period. Randomized clinical trials with human teeth are required in order to determine the suitability of PC before unlimited clinical use can be recommended. PMID:19148409

  6. Fluoxetine Facilitates Fear Extinction Through Amygdala Endocannabinoids

    Science.gov (United States)

    Gunduz-Cinar, Ozge; Flynn, Shaun; Brockway, Emma; Kaugars, Katherine; Baldi, Rita; Ramikie, Teniel S; Cinar, Resat; Kunos, George; Patel, Sachin; Holmes, Andrew

    2016-01-01

    Pharmacologically elevating brain endocannabinoids (eCBs) share anxiolytic and fear extinction-facilitating properties with classical therapeutics, including the selective serotonin reuptake inhibitor, fluoxetine. There are also known functional interactions between the eCB and serotonin systems and preliminary evidence that antidepressants cause alterations in brain eCBs. However, the potential role of eCBs in mediating the facilitatory effects of fluoxetine on fear extinction has not been established. Here, to test for a possible mechanistic contribution of eCBs to fluoxetine's proextinction effects, we integrated biochemical, electrophysiological, pharmacological, and behavioral techniques, using the extinction-impaired 129S1/Sv1mJ mouse strain. Chronic fluoxetine treatment produced a significant and selective increase in levels of anandamide in the BLA, and an associated decrease in activity of the anandamide-catabolizing enzyme, fatty acid amide hydrolase. Slice electrophysiological recordings showed that fluoxetine-induced increases in anandamide were associated with the amplification of eCB-mediated tonic constraint of inhibitory, but not excitatory, transmission in the BLA. Behaviorally, chronic fluoxetine facilitated extinction retrieval in a manner that was prevented by systemic or BLA-specific blockade of CB1 receptors. In contrast to fluoxetine, citalopram treatment did not increase BLA eCBs or facilitate extinction. Taken together, these findings reveal a novel, obligatory role for amygdala eCBs in the proextinction effects of a major pharmacotherapy for trauma- and stressor-related disorders and anxiety disorders. PMID:26514583

  7. Neural signals of vicarious extinction learning.

    Science.gov (United States)

    Golkar, Armita; Haaker, Jan; Selbing, Ida; Olsson, Andreas

    2016-10-01

    Social transmission of both threat and safety is ubiquitous, but little is known about the neural circuitry underlying vicarious safety learning. This is surprising given that these processes are critical to flexibly adapt to a changeable environment. To address how the expression of previously learned fears can be modified by the transmission of social information, two conditioned stimuli (CS + s) were paired with shock and the third was not. During extinction, we held constant the amount of direct, non-reinforced, exposure to the CSs (i.e. direct extinction), and critically varied whether another individual-acting as a demonstrator-experienced safety (CS + vic safety) or aversive reinforcement (CS + vic reinf). During extinction, ventromedial prefrontal cortex (vmPFC) responses to the CS + vic reinf increased but decreased to the CS + vic safety This pattern of vmPFC activity was reversed during a subsequent fear reinstatement test, suggesting a temporal shift in the involvement of the vmPFC. Moreover, only the CS + vic reinf association recovered. Our data suggest that vicarious extinction prevents the return of conditioned fear responses, and that this efficacy is reflected by diminished vmPFC involvement during extinction learning. The present findings may have important implications for understanding how social information influences the persistence of fear memories in individuals suffering from emotional disorders. © The Author (2016). Published by Oxford University Press. For Permissions, please email: journals.permissions@oup.com.

  8. Selection, subdivision and extinction and recolonization.

    Science.gov (United States)

    Cherry, Joshua L

    2004-02-01

    In a subdivided population, the interaction between natural selection and stochastic change in allele frequency is affected by the occurrence of local extinction and subsequent recolonization. The relative importance of selection can be diminished by this additional source of stochastic change in allele frequency. Results are presented for subdivided populations with extinction and recolonization where there is more than one founding allele after extinction, where these may tend to come from the same source deme, where the number of founding alleles is variable or the founders make unequal contributions, and where there is dominance for fitness or local frequency dependence. The behavior of a selected allele in a subdivided population is in all these situations approximately the same as that of an allele with different selection parameters in an unstructured population with a different size. The magnitude of the quantity N(e)s(e), which determines fixation probability in the case of genic selection, is always decreased by extinction and recolonization, so that deleterious alleles are more likely to fix and advantageous alleles less likely to do so. The importance of dominance or frequency dependence is also altered by extinction and recolonization. Computer simulations confirm that the theoretical predictions of both fixation probabilities and mean times to fixation are good approximations.

  9. Mass Extinctions and Biosphere-Geosphere Stability

    Science.gov (United States)

    Rothman, Daniel; Bowring, Samuel

    2015-04-01

    Five times in the past 500 million years, mass extinctions have resulted in the loss of greater than three-fourths of living species. Each of these events is associated with significant environmental change recorded in the carbon-isotopic composition of sedimentary rocks. There are also many such environmental events in the geologic record that are not associated with mass extinctions. What makes them different? Two factors appear important: the size of the environmental perturbation, and the time scale over which it occurs. We show that the natural perturbations of Earth's carbon cycle during the past 500 million years exhibit a characteristic rate of change over two orders of magnitude in time scale. This characteristic rate is consistent with the maximum rate that limits quasistatic (i.e., near steady-state) evolution of the carbon cycle. We identify this rate with marginal stability, and show that mass extinctions occur on the fast, unstable side of the stability boundary. These results suggest that the great extinction events of the geologic past, and potentially a "sixth extinction" associated with modern environmental change, are characterized by common mechanisms of instability.

  10. Quantitative analysis of forest fire extinction efficiency

    Directory of Open Access Journals (Sweden)

    Miguel E. Castillo-Soto

    2015-08-01

    Full Text Available Aim of study: Evaluate the economic extinction efficiency of forest fires, based on the study of fire combat undertaken by aerial and terrestrial means. Area of study, materials and methods: Approximately 112,000 hectares in Chile. Records of 5,876 forest fires that occurred between 1998 and 2009 were analyzed. The area further provides a validation sector for results, by incorporating databases for the years 2010 and 2012. The criteria used for measuring extinction efficiency were economic value of forestry resources, Contraction Factor analysis and definition of the extinction costs function. Main results: It is possible to establish a relationship between burnt area, extinction costs and economic losses. The method proposed may be used and adapted to other fire situations, requiring unit costs for aerial and terrestrial operations, economic value of the property to be protected and speed attributes of fire spread in free advance. Research highlights: The determination of extinction efficiency in containment works of forest fires and potential projection of losses, different types of plant fuel and local conditions favoring the spread of fire broaden the admissible ranges of a, φ and Ce considerably.

  11. Angulation change of the third molar tooth in orthodontic treatment

    Directory of Open Access Journals (Sweden)

    Ardiansyah S. Pawinru

    2017-04-01

    Full Text Available Objective : Impaction of the third molar tooth mandibular is often found in patients with orthodontic treatment. In orthodontic treatment, extraction cases of impaction of the third molar tooth are usually performed, but the patients often refuse this extraction. Extraction of premolar has a good effect on the third molar mandibular angulation during treatment. Material and Methods : This study is a retrospective clinical study with descriptive analytic to find out the effect of the first mandibular premolar tooth extraction to angulation change of the third molar mandibular in orthodontic treatment with a standard edgewise method. Angulation change was performed by comparing the third molar mandibular angulation before and after orthodontic treatment with panoramic radiographs. Angulation of the third molar tooth mandibular was calculated from the angle formed between the long axis of the tooth with the reference line infraorbita. Results : The sample comprised 60 of impacted mandibular third molar region of the left and right regions of 30 patients who had been treated declared cured in clinic of orthodontic specialist of Dentistry Faculty Padjadjaran University. The sample was divided into three (3 groups of patients before treatment angulation of the third molar tooth mandibular under 300, 300 to 600 and above 60o, then measured change of angulation and observed whether it increased, fixed or decreased. Results were analyzed by T- test and Wilcoxon test showed that there was a significant change in angulation of the third molar mandibular in orthodontic treatment with the first premolar tooth mandibular extraction. Conclusion : This study is that the first premolar tooth mandibular extraction affects the angulation of the third molar tooth mandibular after orthodontic treatment.

  12. On the Kendall Correlation Coefficient

    OpenAIRE

    Stepanov, Alexei

    2015-01-01

    In the present paper, we first discuss the Kendall rank correlation coefficient. In continuous case, we define the Kendall rank correlation coefficient in terms of the concomitants of order statistics, find the expected value of the Kendall rank correlation coefficient and show that the later is free of n. We also prove that in continuous case the Kendall correlation coefficient converges in probability to its expected value. We then propose to consider the expected value of the Kendall rank ...

  13. Extinction times of epidemic outbreaks in networks.

    Science.gov (United States)

    Holme, Petter

    2013-01-01

    In the Susceptible-Infectious-Recovered (SIR) model of disease spreading, the time to extinction of the epidemics happens at an intermediate value of the per-contact transmission probability. Too contagious infections burn out fast in the population. Infections that are not contagious enough die out before they spread to a large fraction of people. We characterize how the maximal extinction time in SIR simulations on networks depend on the network structure. For example we find that the average distances in isolated components, weighted by the component size, is a good predictor of the maximal time to extinction. Furthermore, the transmission probability giving the longest outbreaks is larger than, but otherwise seemingly independent of, the epidemic threshold.

  14. Astrophysical life extinctions what killed the dinosaurs?

    CERN Document Server

    Dar, Arnon

    1999-01-01

    Geological records indicate that the exponential diversification of marine and continental life on Earth in the past 500 My was interrupted by many life extinctions. They also indicate that the major mass extinctions were correlated in time with large meteoritic impacts, gigantic volcanic eruptions, sea regressions and drastic changes in global climate. Some of these catastrophes coincided in time. The astrophysical life extinction mechanisms which were proposed so far, in particular, meteoritic impacts, nearby supernova explosions, passage through molecular or dark matter clouds, and Galactic gamma/cosmic ray bursts cannot explain the time coincidences between these catastrophes. However, recent observations suggest that many planetary-mass objects may be present in the outer solar system between the Kuiper belt and the Oort cloud. Gravitational perturbations may occasionally bring them into the inner solar system. Their passage near Earth could have generated gigantic tidal waves, large volcanic eruptions, ...

  15. Biotic extinctions by solar flares; and reply

    International Nuclear Information System (INIS)

    Beland, P.; Russell, D.A.; Crutzen, P.J.; Reid, G.C.

    1976-01-01

    Some comments are offered on the paper by Reid and others (nature 259:177 (1976)) in which a mechanism was suggested by which solar protons might catastrophically deplete atmospheric D 3 during a reversal of the Earth's geomagnetic field. Organisms would thereby be exposed to a more intense UV environment, leading to species extinctions. These authors assumed that during a reversal the geomagnetic field effectively disappears for about 1000 years, and also that solar flares sufficiently intense to cause extinctions occur at intervals of 1000 years or more. The validity of these assumptions is here examined using data on geomagnetic reversals identified over the past 75 M years, together with extinction data, and some anomalies are pointed out. A reply by Reid and others is appended. (U.K.)

  16. The fossil record of the sixth extinction.

    Science.gov (United States)

    Plotnick, Roy E; Smith, Felisa A; Lyons, S Kathleen

    2016-05-01

    Comparing the magnitude of the current biodiversity crisis with those in the fossil record is difficult without an understanding of differential preservation. Integrating data from palaeontological databases with information on IUCN status, ecology and life history characteristics of contemporary mammals, we demonstrate that only a small and biased fraction of threatened species (fossil record, compared with 20% of non-threatened species. We find strong taphonomic biases related to body size and geographic range. Modern species with a fossil record tend to be large and widespread and were described in the 19(th) century. The expected magnitude of the current extinction based only on species with a fossil record is about half of that of one based on all modern species; values for genera are similar. The record of ancient extinctions may be similarly biased, with many species having originated and gone extinct without leaving a tangible record. © 2016 John Wiley & Sons Ltd/CNRS.

  17. Extinction times of epidemic outbreaks in networks.

    Directory of Open Access Journals (Sweden)

    Petter Holme

    Full Text Available In the Susceptible-Infectious-Recovered (SIR model of disease spreading, the time to extinction of the epidemics happens at an intermediate value of the per-contact transmission probability. Too contagious infections burn out fast in the population. Infections that are not contagious enough die out before they spread to a large fraction of people. We characterize how the maximal extinction time in SIR simulations on networks depend on the network structure. For example we find that the average distances in isolated components, weighted by the component size, is a good predictor of the maximal time to extinction. Furthermore, the transmission probability giving the longest outbreaks is larger than, but otherwise seemingly independent of, the epidemic threshold.

  18. Mammal extinctions, body size, and paleotemperature.

    Science.gov (United States)

    Bown, T M; Holroyd, P A; Rose, K D

    1994-10-25

    There is a general inverse relationship between the natural logarithm of tooth area (a body size indicator) of some fossil mammals and paleotemperature during approximately 2.9 million years of the early Eocene in the Bighorn Basin of northwest Wyoming. When mean temperatures became warmer, tooth areas tended to become smaller. During colder times, larger species predominated; these generally became larger or remained the same size. Paleotemperature trends also markedly affected patterns of local (and, perhaps, regional) extinction and immigration. New species appeared as immigrants during or near the hottest (smaller forms) and coldest (larger forms) intervals. Paleotemperature trend reversals commonly resulted in the ultimate extinction of both small forms (during cooling intervals) and larger forms (during warming intervals). These immigrations and extinctions mark faunal turnovers that were also modulated by sharp increases in sediment accumulation rate.

  19. Interstellar extinction in the Taurus dark clouds

    International Nuclear Information System (INIS)

    Meistas, E.; Straizys, V.

    1981-01-01

    The results of photoelectric photometry of 89 stars in the Vilnius seven-color system in the area of the Taurus dark clouds with corrdinates (1950) 4sup(h)16sup(m)-4sup(h)33sup(m), +16 0 -+20 0 are presented. Photometric spectral types, absolute magnitude, color excesses, interstellar extinctions and distances of the stars are determined. The distance of the dark nebula is found to be 140 pc and is in a good agreement with the distance determined for the dark nebula Khavtassi 286, 278. The average extinction Asub(v) in the investigated area is of the order of 1.4. (author)

  20. Tooth Wear Inclination in Great Ape Molars.

    Science.gov (United States)

    Knight-Sadler, Jordan; Fiorenza, Luca

    2017-01-01

    Primate dietary diversity is reflected in their dental morphology, with differences in size and shape of teeth. In particular, the tooth wear angle can provide insight into a species' ability to break down certain foods. To examine dietary and masticatory information, digitized polygon models of dental casts provide a basis for quantitative analysis of wear associated with tooth attrition. In this study, we analyze and compare the wear patterns of Pongo pygmaeus, Gorilla gorillagorilla and Pan troglodytes schweinfurthii lower molars, focusing on the degree of inclination of specific wear facets. The variation in wear angles appears to be indicative of jaw movements and the specific stresses imposed on food during mastication, reflecting thus the ecology of these species. Orangutans exhibit flatter wear angles, more typical of a diet consisting of hard and brittle foods, while gorillas show a wear pattern with a high degree of inclination, reflecting thus their more leafy diet. Chimpanzees, on the other hand, show intermediate inclinations, a pattern that could be related to their highly variable diet. This method is demonstrated to be a powerful tool for better understanding the relationship between food, mastication and tooth wear processes in living primates, and can be potentially used to reconstruct the diet of fossil species. © 2017 S. Karger AG, Basel.

  1. The not-so-harmless maxillary primary first molar extraction.

    Science.gov (United States)

    Northway, W M

    2000-12-01

    Premature loss of primary molars has been associated with space loss and eruptive difficulties, especially when the loss occurs to the primary second molars and when it occurs early. This has not been thought to be the case for primary first molars. The author revisited 13 cases from an earlier study on the effects of premature loss of maxillary primary molars. These longitudinal cases were scrutinized, using serial panoramic radiographs, to explain the irregular response in terms of dental migration. The author presents two case reports. In the earlier study, the author used digitized study casts and the concept of D + E space--the space occupied by the primary first and second molars--to describe the dental migration that occurred after premature tooth loss. Using analysis of variance on data generated using an instrument capable of measuring in tenths of millimeters, the author produced findings regarding the amount of space loss, rate of space loss, effect of age at loss, amount of space regained at the time of replacement by the permanent tooth and effect on Angle's classification. Finally, the author created a simulation describing directional change; this revealed that the maxillary primary first molar loss resulted in a mesial displacement of the permanent canine during eruption. When the maxillary primary first molar is lost prematurely, the first premolar erupts in a more mesial direction than normal, as a result of the mesial incline of the primary second molar, and consumes the space of the permanent canine, which becomes blocked out. Rather than use a space maintainer after the premature loss of the maxillary primary first molar, the author suggests, clinicians can choose from a number of other options for preventing the first premolar from erupting too far in a mesial direction.

  2. A three-dimensional finite element analysis of molar distalization with a palatal plate, pendulum, and headgear according to molar eruption stage

    Science.gov (United States)

    Kang, Ju-Man; Park, Jae Hyun; Bayome, Mohamed; Oh, Moonbee; Park, Chong Ook; Mo, Sung-Seo

    2016-01-01

    Objective This study aimed to (1) evaluate the effects of maxillary second and third molar eruption status on the distalization of first molars with a modified palatal anchorage plate (MPAP), and (2) compare the results to the outcomes of the use of a pendulum and that of a headgear using three-dimensional finite element analysis. Methods Three eruption stages were established: an erupting second molar at the cervical one-third of the first molar root (Stage 1), a fully erupted second molar (Stage 2), and an erupting third molar at the cervical one-third of the second molar root (Stage 3). Retraction forces were applied via three anchorage appliance models: an MPAP with bracket and archwire, a bone-anchored pendulum appliance, and cervical-pull headgear. Results An MPAP showed greater root movement of the first molar than crown movement, and this was more noticeable in Stages 2 and 3. With the other devices, the first molar showed distal tipping. Transversely, the first molar had mesial-out rotation with headgear and mesial-in rotation with the other devices. Vertically, the first molar was intruded with an MPAP, and extruded with the other appliances. Conclusions The second molar eruption stage had an effect on molar distalization, but the third molar follicle had no effect. The application of an MPAP may be an effective treatment option for maxillary molar distalization. PMID:27668192

  3. Autotransplantation of a mandibular third molar: A case report

    Directory of Open Access Journals (Sweden)

    Elham Najafi

    2017-09-01

    Full Text Available Tooth autotransplantation defines as transition of one tooth from one position to another, in same individual. It is a biological procedure in which teeth have the potential to induce alveolar bone growth. It can be applied in patients before adolescence growth is finished. It significantly reduces time and cost compared to implants. Healing rapidly occurs and function is regained almost immediately. Our case was a 15-year-old male that his left mandibular third molar transplanted to the second molar sight after extraction of second molar because of unrestorable crown. During 9 month follow up transplanted tooth was asymptomatic, functional and responsive to sensibility tests. (Cold test, EPT.

  4. Maxillary First Molars with 2 Distobuccal Canals: A Case Series.

    Science.gov (United States)

    Fogel, Howard M; Cunha, Rodrigo Sanches

    2017-11-01

    An appreciation of the anatomic complexity of the root canal system is essential at every step of endodontic treatment. Endodontic treatment of teeth with unusual root canal anatomy presents a unique challenge. Eight patients underwent nonsurgical root canal treatment of 3-rooted maxillary first molars in a specialty endodontic private practice. Four cases of Weine type II and 4 cases of Weine type III canal configurations in the distobuccal root of maxillary first molars were presented.This article highlighted an uncommon anatomic variation of 2 canals in the distobuccal root of the maxillary first molar. Copyright © 2017 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

  5. An aegialodontid upper molar and the evolution of mammal dentition.

    Science.gov (United States)

    Lopatin, Alexey V; Averianov, Alexander O

    2006-08-25

    The most obvious key synapomorphy of the therian mammals is the tribosphenic pattern of their molars. Tribosphenic teeth are capable of both shearing and grinding, which substantially increase effectiveness of food processing and, in turn, permit evolution of a wide range of dietary specializations. Functional tribospheny developed repeatedly during mammalian evolution but was successful only in the Boreosphenida. The earliest stage in the development of boreosphenidan tribospheny has remained poorly understood, being documented only by lower molars of aegialodontids. Here, we report a known upper molar of an aegialodontid mammal, Kielantherium, from the Early Cretaceous of Mongolia.

  6. Theoretical Study of near Neutrality. II. Effect of Subdivided Population Structure with Local Extinction and Recolonization

    Science.gov (United States)

    Ohta, T.

    1992-01-01

    There are several unsolved problems concerning the model of nearly neutral mutations. One is the interaction of subdivided population structure and weak selection that spatially fluctuates. The model of nearly neutral mutations whose selection coefficient spatially fluctuates has been studied by adopting the island model with periodic extinction-recolonization. Both the number of colonies and the migration rate play significant roles in determining mutants' behavior, and selection is ineffective when the extinction-recolonization is frequent with low migration rate. In summary, the number of mutant substitutions decreases and the polymorphism increases by increasing the total population size, and/or decreasing the extinction-recolonization rate. However, by increasing the total size of the population, the mutant substitution rate does not become as low when compared with that in panmictic populations, because of the extinction-recolonization, especially when the migration rate is limited. It is also found that the model satisfactorily explains the contrasting patterns of molecular polymorphisms observed in sibling species of Drosophila, including heterozygosity, proportion of polymorphism and fixation index. PMID:1582566

  7. Reflection coefficients of permeant molecules in human red cell suspensions.

    Science.gov (United States)

    Owen, J D; Eyring, E M

    1975-08-01

    The Staverman reflection coefficient, sigma for several permeant molecules was determined in human red cell suspensions with a Durrum stopped-flow spectrophotometer. This procedure was first used with dog, cat, and beef red cells and with human red cells. The stopped-flow technique used was similar to the rapid-flow method used by those who originally reported sigma measurements in human red cells for molecules which rapidly penetrate the red cell membrane. The sigma values we obtained agreed with those previously reported for most of the slow penetrants, except malonamide, but disagreed with all the sigma values previously reported for the rapid penetrants. We were unable to calculate an "equivalent pore radius" with our sigma data. The advantages of our equipment and our experimental procedure are discussed. Our sigma data suggest that sigma is indirectly proportional to the log of the nonelectrolyte permeability coefficient, omega. Since a similar trend has been previously shown for log omega and molar volume of the permeant molecules, a correlatioo was shown between sigma and molar volume suggesting the membrane acts as a sieve.

  8. ULTRAVIOLET EXTINCTION AT HIGH GALACTIC LATITUDES

    Energy Technology Data Exchange (ETDEWEB)

    Peek, J. E. G.; Schiminovich, David, E-mail: jegpeek@gmail.com [Department of Astronomy, Columbia University, New York, NY (United States)

    2013-07-01

    In order to study the properties and effects of high Galactic latitude dust, we present an analysis of 373,303 galaxies selected from the Galaxy Evolution Explorer All-Sky Survey and Wide-field Infrared Explorer All-Sky Data Release. By examining the variation in aggregate ultraviolet colors and number density of these galaxies, we measure the extinction curve at high latitude. We additionally consider a population of spectroscopically selected galaxies from the Sloan Digital Sky Survey to measure extinction in the optical. We find that dust at high latitude is neither quantitatively nor qualitatively consistent with standard reddening laws. Extinction in the FUV and NUV is {approx}10% and {approx}35% higher than expected, with significant variation across the sky. We find that no single R{sub V} parameter fits both the optical and ultraviolet extinction at high latitude, and that while both show detectable variation across the sky, these variations are not related. We propose that the overall trends we detect likely stem from an increase in very small silicate grains in the interstellar medium.

  9. The Neandertal extinction in eastern Central Europe

    Czech Academy of Sciences Publication Activity Database

    Svoboda, Jiří

    2005-01-01

    Roč. 137, - (2005), s. 69-75 ISSN 1040-6182 Institutional research plan: CEZ:AV0Z80010507 Keywords : Central Europe Neandertals * early modern humans * extinction Subject RIV: AC - Archeology, Anthropology, Ethnology Impact factor: 1.210, year: 2005

  10. ULTRAVIOLET EXTINCTION AT HIGH GALACTIC LATITUDES

    International Nuclear Information System (INIS)

    Peek, J. E. G.; Schiminovich, David

    2013-01-01

    In order to study the properties and effects of high Galactic latitude dust, we present an analysis of 373,303 galaxies selected from the Galaxy Evolution Explorer All-Sky Survey and Wide-field Infrared Explorer All-Sky Data Release. By examining the variation in aggregate ultraviolet colors and number density of these galaxies, we measure the extinction curve at high latitude. We additionally consider a population of spectroscopically selected galaxies from the Sloan Digital Sky Survey to measure extinction in the optical. We find that dust at high latitude is neither quantitatively nor qualitatively consistent with standard reddening laws. Extinction in the FUV and NUV is ∼10% and ∼35% higher than expected, with significant variation across the sky. We find that no single R V parameter fits both the optical and ultraviolet extinction at high latitude, and that while both show detectable variation across the sky, these variations are not related. We propose that the overall trends we detect likely stem from an increase in very small silicate grains in the interstellar medium.

  11. Interstellar Extinction in the Gaia Photometric Systems

    Directory of Open Access Journals (Sweden)

    Bridžius A.

    2003-12-01

    Full Text Available Three medium-band photometric systems proposed for the Gaia space mission are intercompared in determining color excesses for stars of spectral classes from O to M at V = 18 mag. A possibility of obtaining a three-dimensional map of the interstellar extinction is discussed.

  12. Optical atmospheric extinction over Cerro Paranal

    NARCIS (Netherlands)

    Patat, F.; Moehler, S.; O'Brien, K.; Pompei, E.; Bensby, T.; Carraro, G.; de Ugarte Postigo, A.; Fox, A.; Gavignaud, I.; James, G.; Korhonen, H.; Ledoux, C.; Randall, S.; Sana, H.A.A.; Smoker, J.; Stefl, S.; Szeifert, T.

    2011-01-01

    Aims. The present study was conducted to determine the optical extinction curve for Cerro Paranal under typical clear-sky observing conditions, with the purpose of providing the community with a function to be used to correct the observed spectra, with an accuracy of 0.01 mag airmass-1.

  13. A new explanation of the extinction paradox

    International Nuclear Information System (INIS)

    Berg, M.J.; Sorensen, C.M.; Chakrabarti, A.

    2011-01-01

    This work presents a new explanation for the extinction paradox and shows that the canonical explanations are incorrect. This paradox refers to the large size limit of a particle's extinction cross section. It is called a paradox because the geometrical optics approximation, which should be valid in this limit, predicts a cross section that is half of the true value. The new explanation is achieved by formulating the scattered wave in terms of an integral over the particle's surface where the seemingly unrelated Ewald-Oseen theorem appears in the formulation. By expressing the cross section in terms of this surface integral, the Ewald-Oseen theorem is analytically connected to the cross section. Several illustrations are used to reveal the significance of this connection: The paradox is seen to be a consequence of the requirement that the incident wave be canceled within the particle by secondary radiation from its own internal field. Following this, the canonical explanations are examined to reveal serious problems. In the process, the same asymptotic extinction behavior is shown to occur for small highly refractive dielectric particles, and thus is not just a large particle size or small wavelength effect as is often stated. The traditional explanations cannot account for this behavior while the new one actually predicts it. All in all, this work constitutes a fundamental reworking of 60 years of accepted understanding for the cause of the asymptotic behavior of the extinction cross section.

  14. Time to extinction of bird populations

    NARCIS (Netherlands)

    Sæther, B-E.; Engen, S.; Møller, A.P.; Visser, M.E.; Matthysen, E.; Fiedler, W.; Lambrechts, M.M.; Becker, P.H.; Brommer, J.E.; Dickinson, J.; du Feu, C.; Gehlbach, F.R.; Merilä, J.; Rendell, W.; Robertson, R.J.; Thomson, D.L.; Török, J.

    2005-01-01

    The risk of extinction of populations has not previously been empirically related to parameters characterizing their population dynamics. To analyze this relationship, we simulated how the distribution of population dynamical characters changed as a function of time, in both the remaining and the

  15. Methylphenidate Enhances Extinction of Contextual Fear

    Science.gov (United States)

    Abraham, Antony D.; Cunningham, Christopher L.; Lattal, K. Matthew

    2012-01-01

    Methylphenidate (MPH, Ritalin) is a norepinephrine and dopamine transporter blocker that is widely used in humans for treatment of attention deficit disorder and narcolepsy. Although there is some evidence that targeted microinjections of MPH may enhance fear acquisition, little is known about the effect of MPH on fear extinction. Here, we show…

  16. Dust extinction in the first galaxies

    Science.gov (United States)

    Jaacks, Jason; Finkelstein, Steven L.; Bromm, Volker

    2018-04-01

    Using cosmological volume simulations and a custom built sub-grid model for Population III (Pop III) star formation, we examine the baseline dust extinction in the first galaxies due to Pop III metal enrichment in the first billion years of cosmic history. We find that although the most enriched, high-density lines of sight in primordial galaxies can experience a measurable amount of extinction from Pop III dust [E(B - V)max = 0.07, AV, max ≈ 0.28], the average extinction is very low with ≲ 10-3. We derive a power-law relationship between dark matter halo mass and extinction of E(B-V)∝ M_halo^{0.80}. Performing a Monte Carlo parameter study, we establish the baseline reddening of the ultraviolet spectra of dwarf galaxies at high redshift due to Pop III enrichment only. With this method, we find - 2.51 ± 0.07, which is both nearly halo mass and redshift independent.

  17. Stressor controllability modulates fear extinction in humans

    Science.gov (United States)

    Hartley, Catherine A.; Gorun, Alyson; Reddan, Marianne C.; Ramirez, Franchesca; Phelps, Elizabeth A.

    2014-01-01

    Traumatic events are proposed to play a role in the development of anxiety disorders, however not all individuals exposed to extreme stress experience a pathological increase in fear. Recent studies in animal models suggest that the degree to which one is able to control an aversive experience is a critical factor determining its behavioral consequences. In this study, we examined whether stressor controllability modulates subsequent conditioned fear expression in humans. Participants were randomly assigned to an escapable stressor condition, a yoked inescapable stressor condition, or a control condition involving no stress exposure. One week later, all participants underwent fear conditioning, fear extinction, and a test of extinction retrieval the following day. Participants exposed to inescapable stress showed impaired fear extinction learning and increased fear expression the following day. In contrast, escapable stress improved fear extinction and prevented the spontaneous recovery of fear. Consistent with the bidirectional controllability effects previously reported in animal models, these results suggest that one's degree of control over aversive experiences may be an important factor influencing the development of psychological resilience or vulnerability in humans. PMID:24333646

  18. Preformed crowns for decayed primary molar teeth.

    Science.gov (United States)

    Innes, Nicola P T; Ricketts, David; Chong, Lee Yee; Keightley, Alexander J; Lamont, Thomas; Santamaria, Ruth M

    2015-12-31

    Crowns for primary molars are preformed and come in a variety of sizes and materials to be placed over decayed or developmentally defective teeth. They can be made completely of stainless steel (know as 'preformed metal crowns' or PMCs), or to give better aesthetics, may be made of stainless steel with a white veneer cover or made wholly of a white ceramic material. In most cases, teeth are trimmed for the crowns to be fitted conventionally using a local anaesthetic. However, in the case of the Hall Technique, PMCs are pushed over the tooth with no local anaesthetic, carious tissue removal or tooth preparation. Crowns are recommended for restoring primary molar teeth that have had a pulp treatment, are very decayed or are badly broken down. However, few dental practitioners use them in clinical practice. This review updates the original review published in 2007. Primary objectiveTo evaluate the clinical effectiveness and safety of all types of preformed crowns for restoring primary teeth compared with conventional filling materials (such as amalgam, composite, glass ionomer, resin modified glass ionomer and compomers), other types of crowns or methods of crown placement, non-restorative caries treatment or no treatment. Secondary objectiveTo explore whether the extent of decay has an effect on the clinical outcome of primary teeth restored with all types of preformed crowns compared with those restored with conventional filling materials. We searched the following electronic databases: Cochrane Oral Health Group Trials Register (to 21 January 2015), Cochrane Central Register of Controlled Trials (CENTRAL; The Cochrane Library, 2014, Issue 12), MEDLINE via Ovid (1946 to 21 January 2015) and EMBASE via Ovid (1980 to 21 January 2015). We searched the US National Institutes of Health Trials Register (http://clinicaltrials.gov) and the World Health Organization (WHO) International Clinical Trials Registry Platform for ongoing trials and Open Grey for grey literature (to

  19. Biological hierarchies and the nature of extinction.

    Science.gov (United States)

    Congreve, Curtis R; Falk, Amanda R; Lamsdell, James C

    2018-05-01

    Hierarchy theory recognises that ecological and evolutionary units occur in a nested and interconnected hierarchical system, with cascading effects occurring between hierarchical levels. Different biological disciplines have routinely come into conflict over the primacy of different forcing mechanisms behind evolutionary and ecological change. These disconnects arise partly from differences in perspective (with some researchers favouring ecological forcing mechanisms while others favour developmental/historical mechanisms), as well as differences in the temporal framework in which workers operate. In particular, long-term palaeontological data often show that large-scale (macro) patterns of evolution are predominantly dictated by shifts in the abiotic environment, while short-term (micro) modern biological studies stress the importance of biotic interactions. We propose that thinking about ecological and evolutionary interactions in a hierarchical framework is a fruitful way to resolve these conflicts. Hierarchy theory suggests that changes occurring at lower hierarchical levels can have unexpected, complex effects at higher scales due to emergent interactions between simple systems. In this way, patterns occurring on short- and long-term time scales are equally valid, as changes that are driven from lower levels will manifest in different forms at higher levels. We propose that the dual hierarchy framework fits well with our current understanding of evolutionary and ecological theory. Furthermore, we describe how this framework can be used to understand major extinction events better. Multi-generational attritional loss of reproductive fitness (MALF) has recently been proposed as the primary mechanism behind extinction events, whereby extinction is explainable solely through processes that result in extirpation of populations through a shutdown of reproduction. While not necessarily explicit, the push to explain extinction through solely population-level dynamics

  20. Biogeographic and bathymetric determinants of brachiopod extinction and survival during the Late Ordovician mass extinction

    DEFF Research Database (Denmark)

    Finnegan, Seth; Mac Ørum Rasmussen, Christian; Harper, David A. T.

    2016-01-01

    –Early Silurian genus extinctions and evaluate which extinction drivers are best supported by the data. The first (latest Katian) pulse of the LOME preferentially affected genera restricted to deeper waters or to relatively narrow (less than 35°) palaeolatitudinal ranges. This pattern is only observed...... in the latest Katian, suggesting that it reflects drivers unique to this interval. Extinction of exclusively deeper-water genera implies that changes in water mass properties such as dissolved oxygen content played an important role. Extinction of genera with narrow latitudinal ranges suggests that interactions...... between shifting climate zones and palaeobiogeography may also have been important. We test the latter hypothesis by estimating whether each genus would have been able to track habitats within its thermal tolerance range during the greenhouse–icehouse climate transition. Models including these estimates...

  1. Endangered Species and Natural Resource Exploitation: Extinction vs. Coexistence

    OpenAIRE

    Tsur, Yacov; Zemel, Amos

    1994-01-01

    The threat on the survival of animal species due to intensive use of natural resources is incorporated within resource management models, paying special attention to uncertainty regarding the conditions that lead to extinction. The manner in which the potential benefits forgone due to the species extinction (denoted extinction penalty) induce more conservative exploitation policies is studied in detail. When the extinction penalty is ignored, the optimal policy is to drive the resource stock ...

  2. Extinction models for cancer stem cell therapy

    Science.gov (United States)

    Sehl, Mary; Zhou, Hua; Sinsheimer, Janet S.; Lange, Kenneth L.

    2012-01-01

    Cells with stem cell-like properties are now viewed as initiating and sustaining many cancers. This suggests that cancer can be cured by driving these cancer stem cells to extinction. The problem with this strategy is that ordinary stem cells are apt to be killed in the process. This paper sets bounds on the killing differential (difference between death rates of cancer stem cells and normal stem cells) that must exist for the survival of an adequate number of normal stem cells. Our main tools are birth–death Markov chains in continuous time. In this framework, we investigate the extinction times of cancer stem cells and normal stem cells. Application of extreme value theory from mathematical statistics yields an accurate asymptotic distribution and corresponding moments for both extinction times. We compare these distributions for the two cell populations as a function of the killing rates. Perhaps a more telling comparison involves the number of normal stem cells NH at the extinction time of the cancer stem cells. Conditioning on the asymptotic time to extinction of the cancer stem cells allows us to calculate the asymptotic mean and variance of NH. The full distribution of NH can be retrieved by the finite Fourier transform and, in some parameter regimes, by an eigenfunction expansion. Finally, we discuss the impact of quiescence (the resting state) on stem cell dynamics. Quiescence can act as a sanctuary for cancer stem cells and imperils the proposed therapy. We approach the complication of quiescence via multitype branching process models and stochastic simulation. Improvements to the τ-leaping method of stochastic simulation make it a versatile tool in this context. We conclude that the proposed therapy must target quiescent cancer stem cells as well as actively dividing cancer stem cells. The current cancer models demonstrate the virtue of attacking the same quantitative questions from a variety of modeling, mathematical, and computational perspectives

  3. Prediction of postoperative pain after mandibular third molar surgery

    DEFF Research Database (Denmark)

    Rudin, Asa; Eriksson, Lars; Liedholm, Rolf

    2010-01-01

    To evaluate the predictive potential of preoperative psychological and psychophysiological variables in estimating severity of postoperative pain following mandibular third molar surgery (MTMS). Methods: Following ethical committee approval and informed consent, 40 consecutive patients scheduled...

  4. Excess molar volumes and isentropic compressibilities of binary ...

    Indian Academy of Sciences (India)

    Excess molar volume; binary liquid mixtures; isentropic compressibility; intermolecular interactions. ... mixtures are essential for fluid flow, mass flow and heat transfer processes in chemical ... Experimentally determined values of density(ρ).

  5. Evaluation of radiographic features of embedded primary molar ...

    African Journals Online (AJOL)

    2014-05-20

    May 20, 2014 ... Key words: Ankylosis, panoramic radiography, primary molar root ... coverage of the jaws is needed for diagnosis. ... and direct continuity of the bone, called as bony ankylosis. .... Floating retained root lesion mimicking.

  6. Cementoblastoma Relating to Right Mandibular Second Primary Molar

    Directory of Open Access Journals (Sweden)

    Sivakumar Nuvvula

    2016-01-01

    Full Text Available Cementoblastoma is a benign lesion of the odontogenic ectomesenchymal origin. It rarely occurs in primary dentition. This report describes a case of a cementoblastoma relating to the right mandibular second primary molar in a 7-year-old girl. Her panoramic radiograph revealed a well-defined radiopaque lesion with a radiolucent border extending from the distal surface of the mandibular right first primary molar to the distal surface of mandibular second primary molar. The tumor was attached to the mesial root of primary second molar and was excised along with the teeth involved and sent for histopathological evaluation, which showed irregular trabeculae of mineralized tissue interspersed with fibrovascular connective tissue, trabeculae of mineralized tissue with prominent reversal lines, and peripheral rimming of the mineralized tissue with blast cells. On a six-month follow-up, there has been no recurrence of the lesion.

  7. Study of Kissing Molars in Turkish Population Sample

    African Journals Online (AJOL)

    2017-06-28

    Jun 28, 2017 ... unerupted teeth; retention of the mandibular second molar is ... and November 2014 for surgical treatment retrospectively were evaluated. The cases of ... and treatment. Results: Of the 6570 radiographs included in the study,.

  8. Impacted Mandibular Third Molars: Review of Literature and a ...

    African Journals Online (AJOL)

    were screened, and 50 articles were included in the review. Causes of ... impaction rate is higher for third molars when compared with other teeth. The mandibular .... Hence, the surgical extraction of these impacted teeth has become the most ...

  9. Quadrature formulas for Fourier coefficients

    KAUST Repository

    Bojanov, Borislav

    2009-09-01

    We consider quadrature formulas of high degree of precision for the computation of the Fourier coefficients in expansions of functions with respect to a system of orthogonal polynomials. In particular, we show the uniqueness of a multiple node formula for the Fourier-Tchebycheff coefficients given by Micchelli and Sharma and construct new Gaussian formulas for the Fourier coefficients of a function, based on the values of the function and its derivatives. © 2009 Elsevier B.V. All rights reserved.

  10. Malthusian Catastrophe: Species Extinction Caused By Oversized Population

    OpenAIRE

    Pan, Xubin

    2017-01-01

    There is one pseudo-extinction debt and four occurring conditions for real extinction debt. Since small and oversized populations have a high extinction risk, Pan threshold (upper limit) was calculated for Verhulst-Pear logistic growth model and logistic model with the Allee effect, an important parameter corresponding to Allee threshold (lower limit).

  11. Fibroblast Growth Factor-2 Alters the Nature of Extinction

    Science.gov (United States)

    Graham, Bronwyn M.; Richardson, Rick

    2011-01-01

    These experiments examined the effects of the NMDA-receptor (NMDAr) antagonist MK801 on reacquisition and re-extinction of a conditioned fear that had been previously extinguished before injection of fibroblast growth factor-2 (FGF2) or vehicle. Recent findings have shown that relearning and re-extinction, unlike initial learning and extinction,…

  12. Inhibition of Estradiol Synthesis Impairs Fear Extinction in Male Rats

    Science.gov (United States)

    Graham, Bronwyn M.; Milad, Mohammed R.

    2014-01-01

    Emerging research has demonstrated that the sex hormone estradiol regulates fear extinction in female rodents and women. Estradiol may also regulate fear extinction in males, given its role in synaptic plasticity in both sexes. Here we report that inhibition of estradiol synthesis during extinction training, via the aromatase inhibitor fadrozole,…

  13. Slower Reacquisition after Partial Extinction in Human Contingency Learning

    Science.gov (United States)

    Morís, Joaquín; Barberia, Itxaso; Vadillo, Miguel A.; Andrades, Ainhoa; López, Francisco J.

    2017-01-01

    Extinction is a very relevant learning phenomenon from a theoretical and applied point of view. One of its most relevant features is that relapse phenomena often take place once the extinction training has been completed. Accordingly, as extinction-based therapies constitute the most widespread empirically validated treatment of anxiety disorders,…

  14. A study of the fundamental characteristics of 2175A extinction

    Science.gov (United States)

    Cardelli, Jason A.; Savage, Blair D.

    1987-01-01

    The characteristics of interstellar extinction were studied in the region of the 2175 A feature for lines of sight which appear to exhibit unusually weak ultraviolet extinction. The analysis was based upon a parameterization of the observed extinction via fitting specific mathematical functions in order to determine the position and width of the 2175 A feature. The data are currently being analyzed.

  15. Selecting for extinction: nonrandom disease-associated extinction homogenizes amphibian biotas.

    Science.gov (United States)

    Smith, Kevin G; Lips, Karen R; Chase, Jonathan M

    2009-10-01

    Studying the patterns in which local extinctions occur is critical to understanding how extinctions affect biodiversity at local, regional and global spatial scales. To understand the importance of patterns of extinction at a regional spatial scale, we use data from extirpations associated with a widespread pathogenic agent of amphibian decline, Batrachochytrium dendrobatidis (Bd) as a model system. We apply novel null model analyses to these data to determine whether recent extirpations associated with Bd have resulted in selective extinction and homogenization of diverse tropical American amphibian biotas. We find that Bd-associated extinctions in this region were nonrandom and disproportionately, but not exclusively, affected low-occupancy and endemic species, resulting in homogenization of the remnant amphibian fauna. The pattern of extirpations also resulted in phylogenetic homogenization at the family level and ecological homogenization of reproductive mode and habitat association. Additionally, many more species were extirpated from the region than would be expected if extirpations occurred randomly. Our results indicate that amphibian declines in this region are an extinction filter, reducing regional amphibian biodiversity to highly similar relict assemblages and ultimately causing amplified biodiversity loss at regional and global scales.

  16. Coefficient Alpha: A Reliability Coefficient for the 21st Century?

    Science.gov (United States)

    Yang, Yanyun; Green, Samuel B.

    2011-01-01

    Coefficient alpha is almost universally applied to assess reliability of scales in psychology. We argue that researchers should consider alternatives to coefficient alpha. Our preference is for structural equation modeling (SEM) estimates of reliability because they are informative and allow for an empirical evaluation of the assumptions…

  17. Coefficient estimates of negative powers and inverse coefficients for ...

    Indian Academy of Sciences (India)

    and the inequality is sharp for the inverse of the Koebe function k(z) = z/(1 − z)2. An alternative approach to the inverse coefficient problem for functions in the class S has been investigated by Schaeffer and Spencer [27] and FitzGerald [6]. Although, the inverse coefficient problem for the class S has been completely solved ...

  18. Measuring of heat transfer coefficient

    DEFF Research Database (Denmark)

    Henningsen, Poul; Lindegren, Maria

    Subtask 3.4 Measuring of heat transfer coefficient Subtask 3.4.1 Design and setting up of tests to measure heat transfer coefficient Objective: Complementary testing methods together with the relevant experimental equipment are to be designed by the two partners involved in order to measure...... the heat transfer coefficient for a wide range of interface conditions in hot and warm forging processes. Subtask 3.4.2 Measurement of heat transfer coefficient The objective of subtask 3.4.2 is to determine heat transfer values for different interface conditions reflecting those typically operating in hot...

  19. Fusion or gemination? An unusual mandibular second molar

    Directory of Open Access Journals (Sweden)

    Angela Jordão Camargo

    2016-01-01

    Full Text Available Fusion and gemination is not an uncommon finding and affected most primary dentition and the permanent maxillary incisors. These changes can develop a series of complication. A 11-year-old male presented radiography finding: an unusual mandibular second molar. A well-documented case brings a challenge for radiologists classify between fusion and gemination. In conclusion, this alteration although common in other regions, there are no case in the literature involving “second and third” molar.

  20. Managing molar-incisor hypomineralization: A systematic review.

    Science.gov (United States)

    Elhennawy, Karim; Schwendicke, Falk

    2016-12-01

    We systematically reviewed treatment modalities for MIH-affected molars and incisors. Trials on humans with ≥1 MIH molar/incisor reporting on various treatments were included. Two authors independently searched and extracted records. Sample-size-weighted annual failure rates were estimated where appropriate. The risk of bias was assessed using the Newcastle-Ottawa scale. Electronic databases (PubMed, Embase, Cochrane CENTRAL, Google Scholar) were screened, and hand searches and cross-referencing performed. Fourteen (mainly observational) studies were included. Ten trials (381 participants) investigated MIH-molars, four (139) MIH-incisors. For molars, remineralization, restorative or extraction therapies had been assessed. For restorative approaches, mean (SD) annual failure rates were highest for fissure sealants (12[6]%) and glass-ionomer restorations (12[2]%), and lowest for indirect restorations (1[3]%), preformed metal crowns (1.3 [2.1]%) and composite restorations (4[3]%). Ony study assessed extraction of molars in young patients (median age 8.2 years), the majority of them without malocclusions, but third molars in development. Spontaneous alignment of second molars was more frequent in the maxilla (55%) than the mandible (47%). For incisors, desensitizing agents successfully managed hypersensitivity. Micro-abrasion and composite veneers improved aesthetics. Few, mainly moderate to high-risk-studies investigated treatment of MIH. Remineralization or sealants seem suitable for MIH-molars with limited severity and/or hypersensitivity. For severe cases, restorations with composites or indirect restorations or preformed metal crowns seem suitable. Prior to tooth extraction as last resort factors like the presence of a general malocclusion, patients' age and the status of neighboring teeth should be considered. No recommendations can be given for MIH-incisors. Dentists need to consider the specific condition of each tooth and the needs and expectations of

  1. Bilateral maxillary fused second and third molars: a rare occurrence

    OpenAIRE

    Liang, Rui-Zhen; Wu, Jin-Tao; Wu, You-Nong; Smales, Roger J; Hu, Ming; Yu, Jin-Hua; Zhang, Guang-Dong

    2012-01-01

    This case report describes the diagnosis and endodontic therapy of maxillary fused second and third molars, using cone-beam computed tomography (CBCT). A 31-year-old Chinese male, with no contributory medical or family/social history, presented with throbbing pain in the maxillary right molar area following an unsuccessful attempted tooth extraction. Clinical examination revealed what appeared initially to be a damaged large extra cusp on the buccal aspect of the distobuccal cusp of the secon...

  2. Elongational viscosity of narrow molar mass distribution polystyrene

    DEFF Research Database (Denmark)

    Bach, Anders; Almdal, Kristoffer; Rasmussen, Henrik Koblitz

    2003-01-01

    Transient and steady elongational viscosity has been measured for two narrow molar mass distribution polystyrene melts of molar masses 200 000 and 390 000 by means of a filament stretching rheometer. Total Hencky strains of about five have been obtained. The transient elongational viscosity rises...... above the linear viscoelastic prediction at intermediate strains, indicating strain hardening. The steady elongational viscosities are monotone decreasing functions of elongation rate. At elongation rates larger than the inverse reptation time, the steady elongational viscosity scales linearly...

  3. Subcutaneous emphysema during third molar surgery: a case report

    OpenAIRE

    Romeo, Umberto; Galanakis, Alexandros; Lerario, Francesco; Daniele, Gabriele Maria; Tenore, Gianluca; Palaia, Gaspare

    2011-01-01

    Extraction of third molars is the most common surgical procedure performed in oral surgery on a daily basis and, despite surgical skills and expertise, complications may occur. Complications observed during or after third molar removal may include pain, swelling, bleeding, infection, sinus perforation and nerve damage. Fortunately, with a proper management and a good surgical technique, the incidence of such events is low. Subcutaneous emphysema associated with dental extraction occurs when t...

  4. Molar exergy and flow exergy of pure chemical fuels

    International Nuclear Information System (INIS)

    Zanchini, Enzo; Terlizzese, Tiziano

    2009-01-01

    Expressions of the molar exergy and of the molar flow exergy of a pure chemical fuel are deduced rigorously from the basic principles of thermodynamics. It is shown that molar exergy and molar flow exergy coincide when the temperature T and the pressure p of the fuel are equal to the temperature T B and the pressure p B of the environment; a general relation between exergy and flow exergy is proved as a consequence. The deduction of the expression of the molar exergy of a chemical fuel for non-standard values of T B and p B is clarified. For hydrogen, carbon dioxide and several hydrocarbons, tables are reported to allow a simple calculation of the molar exergy of the fuel for any value of the temperature T B and the relative humidity φ B of the environment, in the range 268.15 K ≤ T B ≤ 313.15 K and 0.1 ≤ φ B ≤ 1, with reference to the standard atmospheric pressure. Additional tables are provided to evaluate the difference between the exergy or the flow exergy of the fuel in its given initial state and the exergy at T = T B and p = p B . In these tables, it is assumed that fuel and environment have the same temperature and that the fuel pressure varies in the range 1.01325 bar ≤ p ≤ 200 bar; the fuel may be gas or liquid.

  5. Standard molar enthalpy of formation of methoxyacetophenone isomers

    International Nuclear Information System (INIS)

    Amaral, Luísa M.P.F.; Morais, Victor M.F.; Ribeiro da Silva, Manuel A.V.

    2014-01-01

    Highlights: • Experimental and computational energetic study of methoxyacetophenone isomers. • Enthalpies of formation and phase transition determined by calorimetric techniques. • Quantum chemical calculations allowed estimation of enthalpies of formation. • Structure and energy correlations were established. - Abstract: Values of the standard (p o = 0.1 MPa) molar enthalpy of formation of 2′-, 3′- and 4′-methoxyacetophenones were derived from their standard molar energy of combustion, in oxygen, at T = 298.15 K, measured by static bomb combustion calorimetry. The Calvet high temperature vacuum sublimation technique was used to measure the enthalpies of sublimation/vaporization of the compounds studied. The standard molar enthalpies of formation of the three compounds, in the gaseous phase, at T = 298.15 K, have been derived from the corresponding standard molar enthalpies of formation in the condensed phase and the standard molar enthalpies for the phase transition. The results obtained are −(232.0 ± 2.5), −(237.7 ± 2.7) and −(241.1 ± 2.1) kJ · mol −1 for 2′-, 3′- and 4′-methoxyacetophenone, respectively. Standard molar enthalpies of formation were also estimated from different methodologies: the Cox scheme as well as two different computational approaches using density functional theory-based B3LYP and the multilevel G3 methodologies

  6. Middle mesial canals in mandibular molars: incidence and related factors.

    Science.gov (United States)

    Nosrat, Ali; Deschenes, Raney J; Tordik, Patricia A; Hicks, M Lamar; Fouad, Ashraf F

    2015-01-01

    Although the internal anatomy of mandibular molars has been extensively studied, information about middle mesial (MM) canals is limited. The primary aim of this retrospective study was to evaluate the incidence of MM canals in mandibular first and second molars. The secondary aim was to correlate the incidence of MM canals with variables of molar type, sex, age, ethnicity, and presence of a second distal canal. All mature permanent first and second mandibular molars treated from August 2012 to May 2014 were included in the analysis. After completion of root canal instrumentation in all main canals, the clinician inspected the isthmus area of the mesial root using the dental operating microscope. If there was a catch point in this area with a file or explorer, the operator spent more time attempting to negotiate an MM canal. Seventy-five mandibular first and second molars were treated during the specified period. Fifteen (20%) teeth had negotiable MM canals. The incidence of MM canals was 32.1% in patients ≤ 20 years old, 23.8% in patients 21-40 years old, and 3.8% in patients > 40 years. Analysis of data revealed a significant difference in the distribution of MM canals among different age groups (P molar type, and presence of a second distal canal were not significant. The incidence of negotiable MM canals overall and their frequency of identification in younger patients were higher than in previous reports. Copyright © 2015 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

  7. Cuartos molares supernumerarios: relato de caso clínico

    Directory of Open Access Journals (Sweden)

    Daniela Nascimento Silva

    2006-04-01

    Full Text Available Los dientes supernumerarios se diagnostican mediante exámenes radiográficos de rutina, pues generalmente son asintomáticos. Los cuartos molares representan el segundo grupo de dientes supernumerarios con más frecuencias; ocurren en posición distal a los terceros molares, especialmente en el maxilar superior, y en la mayoría de casos, estos están incluidos. El objetivo de este artículo es realizar la presentación de un caso, de una mujer de 30 anos con los cuartos molares incluidos en el maxilar inferior y describir la técnica para su remoción.Supernumerary teeth are generally asymptomatic and are diagnosed by routine X-ray tests. The fourth molar teeth represent the second group of the most frequent supernumerary teeth, occur in distal position to the third molar teeth, specially in the superior maxilla and, in most of the cases, they are included. The aim of this paper is to comment on the case of a 30-year-old woman with the fourth molar teeth included in the inferior maxilla and to describe the technique used for their removal.

  8. Prevalence of missing and impacted third molars in adults aged 25 years and above

    Science.gov (United States)

    Jung, Yun-Hoa

    2013-01-01

    Purpose The purpose of this study was to determine the prevalence of missing and impacted third molars in people aged 25 years and above. Materials and Methods The study sample of 3,799 patients was chosen randomly from patients who visited Pusan National University Dental Hospital and had panoramic radiographs taken. The data collected included presence and impaction state, angulation, and depth of impaction of third molars, and radiographically detected lesions of third molars and adjacent second molars. Results A greater percentage of men than women retained at least one third molar. The incidence of third molars decreased with increasing age. The incidence of partially impacted third molars greatly declined after the age of 30. Vertically impacted maxillary third molars and horizontally impacted mandibular third molars were most frequent in all age groups. Among the maxillary third molars, those impacted below the cervical line of the second molar were most frequent in all age groups, and among the mandibular third molars, deeply impacted third molars were most frequent in those aged over 40. Dental caries was the most common radiographic lesion of the third molars. Mesioangularly impacted third molars showed radiographic lesions in 13 (9.5%) adjacent maxillary second molars and 117 (27.4%) mandibular second molars. Conclusion The number of remaining third molars decreased and the percentage of Class C depth increased with age. Caries was the most frequent lesion in third molars. Partially impacted mesioangular third molars showed a high incidence of caries or periodontal bone loss of the adjacent second molar. Regular oral examination will be essential to keep asymptomatic third molars in good health. PMID:24380060

  9. Prevalence of missing and impacted third molars in adults aged 25 years and above

    Energy Technology Data Exchange (ETDEWEB)

    Jung, Yun Hoa; Cho, Bong Hae [Dept. of Oral and Maxillofacial Radiology, School of Dentistry, Pusan National University, Yansan (Korea, Republic of)

    2013-12-15

    The purpose of this study was to determine the prevalence of missing and impacted third molars in people aged 25 years and above. The study sample of 3,799 patients was chosen randomly from patients who visited Pusan National University Dental Hospital and had panoramic radiographs taken. The data collected included presence and impaction state, angulation, and depth of impaction of third molars, and radiographically detected lesions of third molars and adjacent second molars. A greater percentage of men than women retained at least one third molar. The incidence of third molars decreased with increasing age. The incidence of partially impacted third molars greatly declined after the age of 30. Vertically impacted maxillary third molars and horizontally impacted mandibular third molars were most frequent in all age groups. Among the maxillary third molars, those impacted below the cervical line of the second molar were most frequent in all age groups, and among the mandibular third molars, deeply impacted third molars were most frequent in those aged over 40. Dental caries was the most common radiographic lesion of the third molars. Mesioangularly impacted third molars showed radiographic lesions in 13 (9.5%) adjacent maxillary second molars and 117 (27.4%) mandibular second molars. The number of remaining third molars decreased and the percentage of Class C depth increased with age. Caries was the most frequent lesion in third molars. Partially impacted mesioangular third molars showed a high incidence of caries or periodontal bone loss of the adjacent second molar. Regular oral examination will be essential to keep asymptomatic third molars in good health.

  10. Prevalence of missing and impacted third molars in adults aged 25 years and above

    International Nuclear Information System (INIS)

    Jung, Yun Hoa; Cho, Bong Hae

    2013-01-01

    The purpose of this study was to determine the prevalence of missing and impacted third molars in people aged 25 years and above. The study sample of 3,799 patients was chosen randomly from patients who visited Pusan National University Dental Hospital and had panoramic radiographs taken. The data collected included presence and impaction state, angulation, and depth of impaction of third molars, and radiographically detected lesions of third molars and adjacent second molars. A greater percentage of men than women retained at least one third molar. The incidence of third molars decreased with increasing age. The incidence of partially impacted third molars greatly declined after the age of 30. Vertically impacted maxillary third molars and horizontally impacted mandibular third molars were most frequent in all age groups. Among the maxillary third molars, those impacted below the cervical line of the second molar were most frequent in all age groups, and among the mandibular third molars, deeply impacted third molars were most frequent in those aged over 40. Dental caries was the most common radiographic lesion of the third molars. Mesioangularly impacted third molars showed radiographic lesions in 13 (9.5%) adjacent maxillary second molars and 117 (27.4%) mandibular second molars. The number of remaining third molars decreased and the percentage of Class C depth increased with age. Caries was the most frequent lesion in third molars. Partially impacted mesioangular third molars showed a high incidence of caries or periodontal bone loss of the adjacent second molar. Regular oral examination will be essential to keep asymptomatic third molars in good health.

  11. Partial molar volumes and partial molar adiabatic compressibilities of a short chain perfluorosurfactant: Sodium heptafluorobutyrate in aqueous solutions at different temperatures

    International Nuclear Information System (INIS)

    Blanco, Elena; Ruso, Juan M.; Prieto, Gerardo; Sarmiento, Felix

    2005-01-01

    Density and ultrasound measurements of sodium heptafluorobutyrate in aqueous solutions at T = (283.15, 288.15, 293.15, 298.15, 303.15, 308.15, 313.15, 318.15, and 323.15) K have been obtained. From these results partial molar volumes and isentropic partial molar adiabatic compressibilities were calculated. Deviations from the Debye-Hueckel limiting law provide evidence for limited association at lower concentrations. The change of the partial molar volume and isentropic partial molar adiabatic compressibility upon aggregation was calculated. Variations of the change of partial molar volumes and isentropic partial molar adiabatic compressibility upon aggregation are discussed in terms of temperature

  12. Partial molar volumes and partial molar adiabatic compressibilities of a short chain perfluorosurfactant: Sodium heptafluorobutyrate in aqueous solutions at different temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Blanco, Elena [Group of Biophysics and Interfaces, Department of Applied Physics, Faculty of Physics, University of Santiago de Compostela, E-15782 Santiago de Compostela (Spain); Ruso, Juan M. [Group of Biophysics and Interfaces, Department of Applied Physics, Faculty of Physics, University of Santiago de Compostela, E-15782 Santiago de Compostela (Spain)]. E-mail: faruso@usc.es; Prieto, Gerardo [Group of Biophysics and Interfaces, Department of Applied Physics, Faculty of Physics, University of Santiago de Compostela, E-15782 Santiago de Compostela (Spain); Sarmiento, Felix [Group of Biophysics and Interfaces, Department of Applied Physics, Faculty of Physics, University of Santiago de Compostela, E-15782 Santiago de Compostela (Spain)

    2005-12-15

    Density and ultrasound measurements of sodium heptafluorobutyrate in aqueous solutions at T = (283.15, 288.15, 293.15, 298.15, 303.15, 308.15, 313.15, 318.15, and 323.15) K have been obtained. From these results partial molar volumes and isentropic partial molar adiabatic compressibilities were calculated. Deviations from the Debye-Hueckel limiting law provide evidence for limited association at lower concentrations. The change of the partial molar volume and isentropic partial molar adiabatic compressibility upon aggregation was calculated. Variations of the change of partial molar volumes and isentropic partial molar adiabatic compressibility upon aggregation are discussed in terms of temperature.

  13. Viscous slip coefficients for binary gas mixtures measured from mass flow rates through a single microtube

    Science.gov (United States)

    Yamaguchi, H.; Takamori, K.; Perrier, P.; Graur, I.; Matsuda, Y.; Niimi, T.

    2016-09-01

    The viscous slip coefficient for helium-argon binary gas mixture is extracted from the experimental values of the mass flow rate through a microtube. The mass flow rate is measured by the constant-volume method. The viscous slip coefficient was obtained by identifying the measured mass flow rate through a microtube with the corresponding analytical expression, which is a function of the Knudsen number. The measurements were carried out in the slip flow regime where the first-order slip boundary condition can be applied. The measured viscous slip coefficients of binary gas mixtures exhibit a concave function of the molar ratio of the mixture, showing a similar profile with numerical results. However, from the detailed comparison between the measured and numerical values with the complete and incomplete accommodation at a surface, it is inappropriate to estimate the viscous slip coefficient for the mixture numerically by employing separately measured tangential momentum accommodation coefficient for each component. The time variation of the molar ratio in the downstream chamber was measured by sampling the gas from the chamber using the quadrupole mass spectrometer. In our measurements, it is indicated that the volume flow rate of argon is larger than that of helium because of the difference in the tangential momentum accommodation coefficient.

  14. Decline and local extinction of Fucales in French Riviera: the harbinger of future extinctions?

    Directory of Open Access Journals (Sweden)

    T. THIBAUT

    2014-03-01

    Full Text Available The French Riviera is one of the Mediterranean areas that has been longest and most thoroughly impacted by human activities. Fucales are long-lived, large-sized brown algae that constitute a good model for studying human impact on species diversity. We gathered all historical data (literature and herbarium vouchers, since the early 19th century, to reconstruct their distribution. The current distribution was established from a 7-year (2007-2013 survey of the 212-km shoreline (1/2 500 map, by means of boating, snorkelling and scuba diving. Overall, 18 taxa of Cystoseira and Sargassum have been reported. Upon comparison with historical data, 5 taxa were no longer observed (C. elegans, C. foeniculacea f. latiramosa, C. squarrosa, C. spinosa var. spinosa and S. hornschuchii while C. jabukae, previously unrecorded, was observed. In addition to these  taxa, probably extinct at a local scale, some taxa had suffered a dramatic decline (C. barbata f. barbata, C. crinita, C. spinosa var. compressa and S. acinarium or become nearly extinct (C. foeniculacea f. tenuiramosa. Three of them, which played in the past significant functional roles in coastal communities, can be considered as functionally extinct. Possible causes of decline and local extinction are discussed. A similar situation has already been reported, although at a much more local scale, in a variety of Mediterranean localities. The question therefore arises about the status of Fucales species in the Mediterranean: are some species on the brink of extinction? Is their extinction at the scale of the French Riviera the harbinger of their extinction Mediterranean–wide?

  15. Orthodontic Replacement of Lost Permanent Molar with Neighbor Molar: A Six-Year Follow-Up

    Directory of Open Access Journals (Sweden)

    Taisa Boamorte Raveli

    2017-01-01

    Full Text Available Extraction is very frequent indication in orthodontic planning, especially when there are crowding, biprotrusion, and aesthetically unpleasant profiles. Next to extraction comes space closure, which represents a challenge for orthodontists because of extended treatment time, discomfort created for the patient, tissue tolerance, and stability concerns. When it comes to what mechanics to choose for space closure, loops present two major advantages in relation to sliding mechanics: absence of abrasion and possibility to reach pure dental translation. A case is presented where an adult female patient with early loss of the first lower permanent molars, minor lower crowding, and tooth biprotrusion was treated with upper first bicuspids extraction along with upper and lower space closure done with T-loops to promote best space closure control in order to correct the malocclusion and enhance facial aesthetics.

  16. Orthodontic Replacement of Lost Permanent Molar with Neighbor Molar: A Six-Year Follow-Up

    Science.gov (United States)

    Shintcovsk, Ricardo Lima; Knop, Luegya Amorim Henriques; Sampaio, Luana Paz

    2017-01-01

    Extraction is very frequent indication in orthodontic planning, especially when there are crowding, biprotrusion, and aesthetically unpleasant profiles. Next to extraction comes space closure, which represents a challenge for orthodontists because of extended treatment time, discomfort created for the patient, tissue tolerance, and stability concerns. When it comes to what mechanics to choose for space closure, loops present two major advantages in relation to sliding mechanics: absence of abrasion and possibility to reach pure dental translation. A case is presented where an adult female patient with early loss of the first lower permanent molars, minor lower crowding, and tooth biprotrusion was treated with upper first bicuspids extraction along with upper and lower space closure done with T-loops to promote best space closure control in order to correct the malocclusion and enhance facial aesthetics. PMID:29318054

  17. Standardised studies on Molar Incisor Hypomineralisation (MIH) and Hypomineralised Second Primary Molars (HSPM): a need.

    Science.gov (United States)

    Elfrink, M E C; Ghanim, A; Manton, D J; Weerheijm, K L

    2015-06-01

    In November 2014, a review of literature concerning prevalence data of Molar Incisor Hypomineralisation (MIH) and Hypomineralised Second Primary Molars (HSPM) was performed. A search of PubMed online databases was conducted for relevant articles published until November 2014. The reference lists of all retrieved articles were hand-searched. Studies were included after assessing the eligibility of the full-text article. Out of 1078 manuscripts, a total of 157 English written publications were selected based on title and abstract. Of these 157, 60 were included in the study and allocated as 52 MIH and 5 HSPM, and 3 for both MIH and HSPM. These studies utilised the European Academy of Paediatric Dentistry judgment criteria, the modified index of developmental defects of enamel (mDDE) and self-devised criteria, and demonstrated a wide variation in the reported prevalence (MIH 2.9-44 %; HSPM 0-21.8 %). Most values mentioned were representative for specific areas. More studies were performed in cities compared with rural areas. A great variation was found in calibration methods, number of participants, number of examiners and research protocols between the studies. The majority of the prevalence studies also investigated possible aetiological factors. To compare MIH and HSPM prevalence and or aetiological data around the world, standardisation of such studies seems essential. Standardisation of the research protocol should include a clearly described sample of children (minimum number of 300 for prevalence and 1000 for aetiology studies) and use of the same calibration sets and methods whereas aetiological studies need to be prospective in nature. A standardised protocol for future MIH and HSPM prevalence and aetiology studies is recommended.

  18. Reactivated Memories Compete for Expression After Pavlovian Extinction

    Science.gov (United States)

    Laborda, Mario A.; Miller, Ralph R.

    2012-01-01

    We view the response decrement resulting from extinction treatment as an interference effect, in which the reactivated memory from acquisition competes with the reactivated memory from extinction for behavioral expression. For each of these memories, reactivation is proportional to both the strength of the stimulus-outcome association and the quality of the facilitatory cues for that association which are present at test. Here we review basic extinction and recovery-from-extinction phenomena, showing how these effects are explicable in this associative interference framework. Moreover, this orientation has and continues to dictate efficient manipulations for minimizing recovery from extinction. This in turn suggests procedures that might reduce relapse from exposure therapy for a number of psychological disorders. Some of these manipulations enhance the facilitatory cues from extinction that are present at test, others strengthen the extinction association (i.e., CS-no outcome), and yet others seem to work by a combination of these two processes. PMID:22326812

  19. Running from fear: Exercise modulation of fear extinction.

    Science.gov (United States)

    Tanner, Margaret K; Hake, Holly S; Bouchet, Courtney A; Greenwood, Benjamin N

    2018-03-31

    Extinction-based exposure therapy is the most common behavioral therapy for anxiety and trauma-related disorders, but fear tends to resurface even after successful extinction. Identification of novel strategies to enhance fear extinction and reduce fear relapse is of paramount importance to mental health. Exercise can enhance cognitive function, but it is not yet well understood whether exercise can be an effective augmentation strategy for fear extinction. In the current review, we present the current state of knowledge on the effects of exercise on fear extinction. Effects of exercise duration, explanations for conflicting results, and potential mechanisms, focusing on a hypothesized role for dopamine, are all discussed. We also provide new data suggesting that the timing in which acute exercise occurs relative to fear extinction, is a crucial variable in determining whether exercise can enhance fear extinction. Clinical implications and ideas to guide future research endeavors in this area are provided. Copyright © 2018 Elsevier Inc. All rights reserved.

  20. A global synthesis of plant extinction rates in urban areas.

    Science.gov (United States)

    Hahs, Amy K; McDonnell, Mark J; McCarthy, Michael A; Vesk, Peter A; Corlett, Richard T; Norton, Briony A; Clemants, Steven E; Duncan, Richard P; Thompson, Ken; Schwartz, Mark W; Williams, Nicholas S G

    2009-11-01

    Plant extinctions from urban areas are a growing threat to biodiversity worldwide. To minimize this threat, it is critical to understand what factors are influencing plant extinction rates. We compiled plant extinction rate data for 22 cities around the world. Two-thirds of the variation in plant extinction rates was explained by a combination of the city's historical development and the current proportion of native vegetation, with the former explaining the greatest variability. As a single variable, the amount of native vegetation remaining also influenced extinction rates, particularly in cities > 200 years old. Our study demonstrates that the legacies of landscape transformations by agrarian and urban development last for hundreds of years, and modern cities potentially carry a large extinction debt. This finding highlights the importance of preserving native vegetation in urban areas and the need for mitigation to minimize potential plant extinctions in the future.

  1. Role of the hippocampus in contextual modulation of fear extinction

    Institute of Scientific and Technical Information of China (English)

    Lingzhi Kong; Xihong Wu; Liang Li

    2008-01-01

    Fear extinction is an important form of emotional learning, and affects neural plasticity. Cue fear extinction is a classical form of inhibitory learning that can be used as an exposure-based treatment for phobia, because the long-term extinction memory produced during cue fear extinction can limit the over-expression of fear. The expression of this inhibitory memory partly depends on the context in which the extinction learning occurs. Studies such as transient inhibition, electrophysiology and brain imaging have proved that the hippocampus - an important structure in the limbic system - facilitates memory retrieval by contextual cues.Mediation of the hippocampus-medial prefrontal lobe circuit may be the neurobiological basis of this process.This article has reviewed the role of the hippocampus in the learning and retrieval of fear extinction.Contextual modulation of fear extinction may rely on a neural network consisting of the hippocampus, the medial prefrontal cortex and the amygdala.

  2. Aspartic acid racemization in dentin of the third molar for age estimation of the Chaoshan population in South China.

    Science.gov (United States)

    Chen, Shisheng; Lv, Yanyi; Wang, Dian; Yu, Xiaojun

    2016-09-01

    Aspartic acid racemization in teeth has been increasingly used to estimate chronological age with a considerably high accuracy in forensic practice. The Chaoshan population in South China is relatively isolated in geography, and has specific lifestyle and dietary inhibits. It is still unknown whether this method is suitable for this population. The aim of this study was to analyze the relationship between chronological age and the d/l aspartic acid ratio in dentin in the third molar tooth of the Chaoshan population. Fifty-eight non-carious third molar teeth (31 mandibles and 27 maxillae), from 58 living individuals of known age (24 males and 34 females), were retrieved. Dentin was extracted from these teeth. The d- and l-aspartic acids in dentins were separated and detected by high performance liquid chromatography (HPLC). Linear regression was performed between the d/l aspartic acid ratio of dentins and chronological age. Results showed that the correlation coefficient (r) was 0.969, and the mean absolute error (MAE) was 2.19 years, its standard deviation (SD) was ±1.53 years, indicating excellent correlation. There was no significant difference in racemization rates of dentin between sexes (P=0.113, F=2.6), or between mandibles and maxillae (P=0.964, F=0.000). Results indicate that the ratio of the d and l forms of aspartic acid of dentins, in the third molar, is closely correlated with chronological age, special lifestyle do no obviously affect the accuracy of the age estimations by aspartic acid racemization of the dentin in the third molar and that aspartic acid racemization in the third molar dentin can be used as an accurate method to estimate chronological age in the Chaoshan population in South China. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

  3. Epidemic extinction paths in complex networks

    Science.gov (United States)

    Hindes, Jason; Schwartz, Ira B.

    2017-05-01

    We study the extinction of long-lived epidemics on finite complex networks induced by intrinsic noise. Applying analytical techniques to the stochastic susceptible-infected-susceptible model, we predict the distribution of large fluctuations, the most probable or optimal path through a network that leads to a disease-free state from an endemic state, and the average extinction time in general configurations. Our predictions agree with Monte Carlo simulations on several networks, including synthetic weighted and degree-distributed networks with degree correlations, and an empirical high school contact network. In addition, our approach quantifies characteristic scaling patterns for the optimal path and distribution of large fluctuations, both near and away from the epidemic threshold, in networks with heterogeneous eigenvector centrality and degree distributions.

  4. Extinction of corrugated hydrogen/air flames

    International Nuclear Information System (INIS)

    Mizomoto, M.; Asaka, Y.; Ikai, S.; Law, C.K.

    1982-01-01

    Recent studies on flammability limits reveal the importance of flow nonuniformity, flame curvature, and molecular and thermal diffusivities in determining the extinguishability and the associated limits of premixed fuel/air flames. In particular, it is found that conditions which favor extinction of a lean flame may cause intensification of a rich flame. In the present study the authors have experimentally determined the extinction characteristics and limits of highly curved hydrogen/air flames as represented by the opening of bunsen flame tips. Results show that the tip opens at a constant fuel equivalence ratio of phi = 1.15, regardless of the velocity and uniformity of the upstream flow. This critical mixture concentration, while being rich, is still on the lean side of that corresponding to the maximum burning velocity (phi = 1.8), implying that for highly diffusive systems, the relevant reference concentration is that for maximum burning velocity instead of stoichiometry

  5. The galactic extinction towards Maffei 1

    International Nuclear Information System (INIS)

    Buta, R.J.; McCall, M.L.; McDonald Observatory, Austin, TX; Australian National Univ., Canberra. Mount Stromlo and Siding Spring Observatories)

    1983-01-01

    The extinction of Maffei 1 has been measured by two new techniques. First, BV aperture photometry has been performed to obtain the colour excess from standard aperture-colour relations for early-type galaxies. Secondly, millimetre and radio observations of galactic CO and HI have been used to calculate the total hydrogen column density along the line-of-sight, and thereby estimate the colour excess from the local dust-to-gas ratio. After consideration of all extinction measurements to date, it is concluded that Asub(v)=5.1+-0.2 mag. The isophotal diameter and the corrected apparent visual magnitude are estimated to be approx. 15 arcmin and approx. 6.3 respectively (assuming type E), making Maffei 1 one of the biggest and brightest galaxies in the sky. (author)

  6. Endodontic treatment of an unusual connation of permanent mandibular molars: a case report.

    Science.gov (United States)

    Liu, Shengbo; Fan, Bing; Peng, Bin; Fan, Mingwen; Bian, Zhuan

    2006-10-01

    A 27-year-old patient with an anomalous mandibular molar was referred for endodontic therapy. Clinical and radiographic examination revealed the connation of a second mandibular molar with a third molar. Challenging endodontic therapy was performed in the unusual connated molars. A 2-year recall showed good treatment result.

  7. Extinction risk under coloured environmental noise

    OpenAIRE

    Heino, M; Ripa, Jörgen; Kaitala, V

    2000-01-01

    Positively autocorrelated red environmental noise is characterized by a strong dependence of expected sample variance on sample length. This dependence has to be taken into account when assessing extinction risk under red and white uncorrelated environmental noise. To facilitate a comparison between red and white noise, their expected variances can be scaled to be equal, but only at a chosen time scale. We show with a simple one-dimensional population dynamics model that the different but equ...

  8. Immunological systematics of the extinct quagga (Equidae).

    Science.gov (United States)

    Lowenstein, J M; Ryder, O A

    1985-09-15

    It has been debated whether the extinct quagga was a distinct fourth species of African zebra or whether it was merely the southern variant of the Plains zebra (Equus burchelli). Using a radioimmunoassay (RIA) technique, we have shown that proteins remaining in quagga skins from museums are much more similar to serum proteins of the Plains zebra than to those of the other two extant zebras.

  9. Rewinding the process of mammalian extinction

    OpenAIRE

    Saragusty, J.; Diecke, S.; Drukker, M.; Durrant, B.; Friedrich Ben-Nun, I.; Galli, C.; Goeritz, F.; Hayashi, K.; Hermes, R.; Holtze, S.; Johnson, S.; Lazzari, G.; Loi, P.; Loring, J.F.; Okita, K.

    2016-01-01

    With only three living individuals left on this planet, the northern white rhinoceros (Ceratotherium simum cottoni) could be considered doomed for extinction. It might still be possible, however, to rescue the (sub)species by combining novel stem cell and assisted reproductive technologies. To discuss the various practical options available to us, we convened a multidisciplinary meeting under the name "Conservation by Cellular Technologies." The outcome of this meeting and the proposed road m...

  10. Opportunities and costs for preventing vertebrate extinctions.

    Science.gov (United States)

    Conde, Dalia A; Colchero, Fernando; Güneralp, Burak; Gusset, Markus; Skolnik, Ben; Parr, Michael; Byers, Onnie; Johnson, Kevin; Young, Glyn; Flesness, Nate; Possingham, Hugh; Fa, John E

    2015-03-16

    Despite an increase in policy and management responses to the global biodiversity crisis, implementation of the 20 Aichi Biodiversity Targets still shows insufficient progress [1]. These targets, strategic goals defined by the United Nations Convention on Biological Diversity (CBD), address major causes of biodiversity loss in part by establishing protected areas (Target 11) and preventing species extinctions (Target 12). To achieve this, increased interventions will be required for a large number of sites and species. The Alliance for Zero Extinction (AZE) [2], a consortium of conservation-oriented organisations that aims to protect Critically Endangered and Endangered species restricted to single sites, has identified 920 species of mammals, birds, amphibians, reptiles, conifers and reef-building corals in 588 'trigger' sites [3]. These are arguably the most irreplaceable category of important biodiversity conservation sites. Protected area coverage of AZE sites is a key indicator of progress towards Target 11 [1]. Moreover, effective conservation of AZE sites is essential to achieve Target 12, as the loss of any of these sites would certainly result in the global extinction of at least one species [2]. However, averting human-induced species extinctions within AZE sites requires enhanced planning tools to increase the chances of success [3]. Here, we assess the potential for ensuring the long-term conservation of AZE vertebrate species (157 mammals, 165 birds, 17 reptiles and 502 amphibians) by calculating a conservation opportunity index (COI) for each species. The COI encompasses a set of measurable indicators that quantify the possibility of achieving successful conservation of a species in its natural habitat (COIh) and by establishing insurance populations in zoos (COIc). Copyright © 2015 Elsevier Ltd. All rights reserved.

  11. Parrots and macaws: Species in extinction danger?

    International Nuclear Information System (INIS)

    Castro ramirez, Jose; Moyano P, Edgar A

    1994-01-01

    The paper refers to the privileged position of Colombia due to their position in the tropic, the influence of two oceans, their wide hydrographic net, variety of climates, etc; they make that Colombia occupies first places in biodiversity; but due to the indiscriminate pruning of primary forest, they make that this enormous biological potential is seriously threatened, where many of its birds are in extinction road

  12. Pattern of third molar impaction in a Saudi population

    Directory of Open Access Journals (Sweden)

    Ali H Hassan

    2010-10-01

    Full Text Available Ali H Hassan11Department of Preventive Dental Sciences, Faculty of Dentistry, King Abdulaziz University, Jeddah, Saudi ArabiaObjective: To evaluate the current pattern of third molar impaction in a sample of Saudi patients.Methods: One thousand thirty-nine orthopantomograms (OPG of patients ranging in age from 19 to 46 years (536 males and 503 females were evaluated to determine the frequency of impacted third molars, their levels of eruption, and their angulations.Results: Four hundred twenty-two (40.5% of the 1039 OPG showed at least one impacted third molar, with no significant difference between males (222; 52.6% and females (200; 47.4% (P = 0.284. The most common number of impacted third molars per OPG was one (72.5%. Impacted third molars were 1.64 times more likely to occur in the mandible than in the maxilla. The most common angulation of impaction in the mandible was the mesial (33.4%, while the most common angulation in the maxilla, was the vertical (49.6%. Level B impaction was the most common in both maxilla (48.2% and mandible (67.7%. There was no significant difference in the frequency of impaction between the right and left sides in both jaws.Conclusion: The pattern of third molar impaction in the western region of Saudi Arabia is characterized by a high prevalence of impaction that is greater in the mandibles and with no sex predilection.Keywords: third molar, impaction, prevalence, Saudi 

  13. Genetic integration of molar cusp size variation in baboons.

    Science.gov (United States)

    Koh, Christina; Bates, Elizabeth; Broughton, Elizabeth; Do, Nicholas T; Fletcher, Zachary; Mahaney, Michael C; Hlusko, Leslea J

    2010-06-01

    Many studies of primate diversity and evolution rely on dental morphology for insight into diet, behavior, and phylogenetic relationships. Consequently, variation in molar cusp size has increasingly become a phenotype of interest. In 2007 we published a quantitative genetic analysis of mandibular molar cusp size variation in baboons. Those results provided more questions than answers, as the pattern of genetic integration did not fit predictions from odontogenesis. To follow up, we expanded our study to include data from the maxillary molar cusps. Here we report on these later analyses, as well as inter-arch comparisons with the mandibular data. We analyzed variation in two-dimensional maxillary molar cusp size using data collected from a captive pedigreed breeding colony of baboons, Papio hamadryas, housed at the Southwest National Primate Research Center. These analyses show that variation in maxillary molar cusp size is heritable and sexually dimorphic. We also estimated additive genetic correlations between cusps on the same crown, homologous cusps along the tooth row, and maxillary and mandibular cusps. The pattern for maxillary molars yields genetic correlations of one between the paracone-metacone and protocone-hypocone. Bivariate analyses of cuspal homologues on adjacent teeth yield correlations that are high or not significantly different from one. Between dental arcades, the nonoccluding cusps consistently yield high genetic correlations, especially the metaconid-paracone and metaconid-metacone. This pattern of genetic correlation does not immediately accord with the pattern of development and/or calcification, however these results do follow predictions that can be made from the evolutionary history of the tribosphenic molar. Copyright 2009 Wiley-Liss, Inc.

  14. Relation between heat of vaporization, ion transport, molar volume, and cation-anion binding energy for ionic liquids.

    Science.gov (United States)

    Borodin, Oleg

    2009-09-10

    A number of correlations between heat of vaporization (H(vap)), cation-anion binding energy (E(+/-)), molar volume (V(m)), self-diffusion coefficient (D), and ionic conductivity for 29 ionic liquids have been investigated using molecular dynamics (MD) simulations that employed accurate and validated many-body polarizable force fields. A significant correlation between D and H(vap) has been found, while the best correlation was found for -log(DV(m)) vs H(vap) + 0.28E(+/-). A combination of enthalpy of vaporization and a fraction of the cation-anion binding energy was suggested as a measure of the effective cohesive energy for ionic liquids. A deviation of some ILs from the reported master curve is explained based upon ion packing and proposed diffusion pathways. No general correlations were found between the ion diffusion coefficient and molecular volume or the diffusion coefficient and cation/anion binding energy.

  15. Sabine absorption coefficients to random incidence absorption coefficients

    DEFF Research Database (Denmark)

    Jeong, Cheol-Ho

    2014-01-01

    into random incidence absorption coefficients for porous absorbers are investigated. Two optimization-based conversion methods are suggested: the surface impedance estimation for locally reacting absorbers and the flow resistivity estimation for extendedly reacting absorbers. The suggested conversion methods...

  16. Pathways to extinction: beyond the error threshold.

    Science.gov (United States)

    Manrubia, Susanna C; Domingo, Esteban; Lázaro, Ester

    2010-06-27

    Since the introduction of the quasispecies and the error catastrophe concepts for molecular evolution by Eigen and their subsequent application to viral populations, increased mutagenesis has become a common strategy to cause the extinction of viral infectivity. Nevertheless, the high complexity of virus populations has shown that viral extinction can occur through several other pathways apart from crossing an error threshold. Increases in the mutation rate enhance the appearance of defective forms and promote the selection of mechanisms that are able to counteract the accelerated appearance of mutations. Current models of viral evolution take into account more realistic scenarios that consider compensatory and lethal mutations, a highly redundant genotype-to-phenotype map, rough fitness landscapes relating phenotype and fitness, and where phenotype is described as a set of interdependent traits. Further, viral populations cannot be understood without specifying the characteristics of the environment where they evolve and adapt. Altogether, it turns out that the pathways through which viral quasispecies go extinct are multiple and diverse.

  17. Interstellar Extinction in 20 Open Star Clusters

    Science.gov (United States)

    Rangwal, Geeta; Yadav, R. K. S.; Durgapal, Alok K.; Bisht, D.

    2017-12-01

    The interstellar extinction law in 20 open star clusters namely, Berkeley 7, Collinder 69, Hogg 10, NGC 2362, Czernik 43, NGC 6530, NGC 6871, Bochum 10, Haffner 18, IC 4996, NGC 2384, NGC 6193, NGC 6618, NGC 7160, Collinder 232, Haffner 19, NGC 2401, NGC 6231, NGC 6823, and NGC 7380 have been studied in the optical and near-IR wavelength ranges. The difference between maximum and minimum values of E(B - V) indicates the presence of non-uniform extinction in all the clusters except Collinder 69, NGC 2362, and NGC 2384. The colour excess ratios are consistent with a normal extinction law for the clusters NGC 6823, Haffner 18, Haffner 19, NGC 7160, NGC 6193, NGC 2401, NGC 2384, NGC 6871, NGC 7380, Berkeley 7, Collinder 69, and IC 4996. We have found that the differential colour-excess ΔE(B - V), which may be due to the occurrence of dust and gas inside the clusters, decreases with the age of the clusters. A spatial variation of colour excess is found in NGC 6193 in the sense that it decreases from east to west in the cluster region. For the clusters Berkeley 7, NGC 7380, and NGC 6871, a dependence of colour excess E(B - V) with spectral class and luminosity is observed. Eight stars in Collinder 232, four stars in NGC 6530, and one star in NGC 6231 have excess flux in near-IR. This indicates that these stars may have circumstellar material around them.

  18. Mathematical Modeling of Extinction of Inhomogeneous Populations

    Science.gov (United States)

    Karev, G.P.; Kareva, I.

    2016-01-01

    Mathematical models of population extinction have a variety of applications in such areas as ecology, paleontology and conservation biology. Here we propose and investigate two types of sub-exponential models of population extinction. Unlike the more traditional exponential models, the life duration of sub-exponential models is finite. In the first model, the population is assumed to be composed clones that are independent from each other. In the second model, we assume that the size of the population as a whole decreases according to the sub-exponential equation. We then investigate the “unobserved heterogeneity”, i.e. the underlying inhomogeneous population model, and calculate the distribution of frequencies of clones for both models. We show that the dynamics of frequencies in the first model is governed by the principle of minimum of Tsallis information loss. In the second model, the notion of “internal population time” is proposed; with respect to the internal time, the dynamics of frequencies is governed by the principle of minimum of Shannon information loss. The results of this analysis show that the principle of minimum of information loss is the underlying law for the evolution of a broad class of models of population extinction. Finally, we propose a possible application of this modeling framework to mechanisms underlying time perception. PMID:27090117

  19. Area-based assessment of extinction risk.

    Science.gov (United States)

    Hei, Fangliang

    2012-05-01

    Underpinning the International Union for Conservation of Nature (IUCN) Red List is the assessment of extinction risk as determined by the size and degree of loss of populations. The IUCN system lists a species as Critically Endangered, Endangered, or Vulnerable if its population size declines 80%, 50%, or 30% within a given time frame. However, effective implementation of the system faces substantial challenges and uncertainty because geographic scale data on population size and long-term dynamics are scarce. I develop a model to quantify extinction risk using a measure based on a species' distribution, a much more readily obtained quantity. The model calculates the loss of the area of occupancy that is equivalent to the loss of a given proportion of a population. It is a very simple yet general model that has no free parameters and is independent of scale. The model predicted well the distributions of 302 tree species at a local scale and the distributions of 348 species of North American land birds. This area-based model provides a solution to the long-standing problem for IUCN assessments of lack of data on population sizes, and thus it will contribute to facilitating the quantification of extinction risk worldwide.

  20. Permo-Triassic vertebrate extinctions: A program

    Science.gov (United States)

    Olson, E. C.

    1988-01-01

    Since the time of the Authors' study on this subject, a great deal of new information has become available. Concepts of the nature of extinctions have changed materially. The Authors' conclusion that a catastrophic event was not responsible for the extinction of vertebrates has modified to the extent that hypotheses involving either the impact of a massive extra-terrestrial body or volcanism provide plausible but not currently fully testable hypotheses. Stated changes resulted in a rapid decrease in organic diversity, as the ratio of origins of taxa to extinctions shifted from strongly positive to negative, with momentary equilibrium being reached at about the Permo-Triassic boundary. The proximate causes of the changes in the terrestrial biota appear to lie in two primary factors: (1) strong climatic changes (global mean temperatures, temperature ranges, humidity) and (2) susceptibility of the dominant vertebrates (large dicynodonts) and the glossopteris flora to disruption of the equlibrium of the world ecosystem. The following proximate causes have been proposed: (1) rhythmic fluctuations in solar radiation, (2) tectonic events as Pangea assembled, altering land-ocean relationships, patterns of wind and water circulation and continental physiography, (3) volcanism, and (4) changes subsequent to impacts of one or more massive extra terrestrial objects, bodies or comets. These hypotheses are discussed.

  1. Rewinding the process of mammalian extinction.

    Science.gov (United States)

    Saragusty, Joseph; Diecke, Sebastian; Drukker, Micha; Durrant, Barbara; Friedrich Ben-Nun, Inbar; Galli, Cesare; Göritz, Frank; Hayashi, Katsuhiko; Hermes, Robert; Holtze, Susanne; Johnson, Stacey; Lazzari, Giovanna; Loi, Pasqualino; Loring, Jeanne F; Okita, Keisuke; Renfree, Marilyn B; Seet, Steven; Voracek, Thomas; Stejskal, Jan; Ryder, Oliver A; Hildebrandt, Thomas B

    2016-07-01

    With only three living individuals left on this planet, the northern white rhinoceros (Ceratotherium simum cottoni) could be considered doomed for extinction. It might still be possible, however, to rescue the (sub)species by combining novel stem cell and assisted reproductive technologies. To discuss the various practical options available to us, we convened a multidisciplinary meeting under the name "Conservation by Cellular Technologies." The outcome of this meeting and the proposed road map that, if successfully implemented, would ultimately lead to a self-sustaining population of an extremely endangered species are outlined here. The ideas discussed here, while centered on the northern white rhinoceros, are equally applicable, after proper adjustments, to other mammals on the brink of extinction. Through implementation of these ideas we hope to establish the foundation for reversal of some of the effects of what has been termed the sixth mass extinction event in the history of Earth, and the first anthropogenic one. Zoo Biol. 35:280-292, 2016. © 2016 The Authors. Zoo Biology published by Wiley Periodicals, Inc. © 2016 The Authors. Zoo Biology published by Wiley Periodicals, Inc.

  2. Causes and timing of future biosphere extinctions

    Directory of Open Access Journals (Sweden)

    S. Franck

    2006-01-01

    Full Text Available We present a minimal model for the global carbon cycle of the Earth containing the reservoirs mantle, ocean floor, continental crust, biosphere, and the kerogen, as well as the combined ocean and atmosphere reservoir. The model is specified by introducing three different types of biosphere: procaryotes, eucaryotes, and complex multicellular life. During the entire existence of the biosphere procaryotes are always present. 2 Gyr ago eucaryotic life first appears. The emergence of complex multicellular life is connected with an explosive increase in biomass and a strong decrease in Cambrian global surface temperature at about 0.54 Gyr ago. In the long-term future the three types of biosphere will die out in reverse sequence of their appearance. We show that there is no evidence for an implosion-like extinction in contrast to the Cambrian explosion. In dependence of their temperature tolerance complex multicellular life and eucaryotes become extinct in about 0.8–1.2 Gyr and 1.3–1.5 Gyr, respectively. The ultimate life span of the biosphere is defined by the extinction of procaryotes in about 1.6 Gyr.

  3. Interstellar extinction and polarization in the infrared

    International Nuclear Information System (INIS)

    Martin, P.G.; Whittet, D.C.B.

    1990-01-01

    The wavelength dependences of interstellar continuum extinction and polarization in the range 0.35-5 microns are examined. The existence of a universal extinction curve with power law index of about 1.8 extending from the near-IR to at least 5 microns appears to be established for both diffuse and dense cloud dust. The polarization yields evidence for some degree of universality in the 1.6-5 micron regime which may be represented by a power law with index 1.5-2.0, encompassing that for extinction. The form of the polarization curve in the IR seems independent of the wavelength at which the degree of polarization peaks in the optical, implying that variations in that wavelength are caused by changes in the optical properties of the particle at blue-visible rather than IR wavelengths. It is argued that the more significant alterations of the grain size distribution from one environment to another occur for the smaller particles. 47 refs

  4. Effect of Audiovisual Treatment Information on Relieving Anxiety in Patients Undergoing Impacted Mandibular Third Molar Removal.

    Science.gov (United States)

    Choi, Sung-Hwan; Won, Ji-Hoon; Cha, Jung-Yul; Hwang, Chung-Ju

    2015-11-01

    The authors hypothesized that an audiovisual slide presentation that provided treatment information regarding the removal of an impacted mandibular third molar could improve patient knowledge of postoperative complications and decrease anxiety in young adults before and after surgery. A group that received an audiovisual description was compared with a group that received the conventional written description of the procedure. This randomized clinical trial included young adult patients who required surgical removal of an impacted mandibular third molar and fulfilled the predetermined criteria. The predictor variable was the presentation of an audiovisual slideshow. The audiovisual informed group provided informed consent after viewing an audiovisual slideshow. The control group provided informed consent after reading a written description of the procedure. The outcome variables were the State-Trait Anxiety Inventory, the Dental Anxiety Scale, a self-reported anxiety questionnaire, completed immediately before and 1 week after surgery, and a postoperative questionnaire about the level of understanding of potential postoperative complications. The data were analyzed with χ(2) tests, independent t tests, Mann-Whitney U  tests, and Spearman rank correlation coefficients. Fifty-one patients fulfilled the inclusion criteria. The audiovisual informed group was comprised of 20 men and 5 women; the written informed group was comprised of 21 men and 5 women. The audiovisual informed group remembered significantly more information than the control group about a potential allergic reaction to local anesthesia or medication and potential trismus (P audiovisual informed group had lower self-reported anxiety scores than the control group 1 week after surgery (P audiovisual slide presentation could improve patient knowledge about postoperative complications and aid in alleviating anxiety after the surgical removal of an impacted mandibular third molar. Copyright © 2015

  5. Accuracy of an equation for estimating age from mandibular third molar development in a Thai population

    International Nuclear Information System (INIS)

    Verochana, Karune; Prapayasatok, Sangsom; Janhom, Apirum; Mahasantipiya, Phattaranant May; Korwanich, Narumanas

    2016-01-01

    This study assessed the accuracy of age estimates produced by a regression equation derived from lower third molar development in a Thai population. The first part of this study relied on measurements taken from panoramic radiographs of 614 Thai patients aged from 9 to 20. The stage of lower left and right third molar development was observed in each radiograph and a modified Gat score was assigned. Linear regression on this data produced the following equation: Y=9.309+1.673 mG+0.303S (Y=age; mG=modified Gat score; S=sex). In the second part of this study, the predictive accuracy of this equation was evaluated using data from a second set of panoramic radiographs (539 Thai subjects, 9 to 24 years old). Each subject's age was estimated using the above equation and compared against age calculated from a provided date of birth. Estimated and known age data were analyzed using the Pearson correlation coefficient and descriptive statistics. Ages estimated from lower left and lower right third molar development stage were significantly correlated with the known ages (r=0.818, 0.808, respectively, P≤0.01). 50% of age estimates in the second part of the study fell within a range of error of ±1 year, while 75% fell within a range of error of ±2 years. The study found that the equation tends to estimate age accurately when individuals are 9 to 20 years of age. The equation can be used for age estimation for Thai populations when the individuals are 9 to 20 years of age

  6. Accuracy of an equation for estimating age from mandibular third molar development in a Thai population.

    Science.gov (United States)

    Verochana, Karune; Prapayasatok, Sangsom; Janhom, Apirum; Mahasantipiya, Phattaranant May; Korwanich, Narumanas

    2016-03-01

    This study assessed the accuracy of age estimates produced by a regression equation derived from lower third molar development in a Thai population. The first part of this study relied on measurements taken from panoramic radiographs of 614 Thai patients aged from 9 to 20. The stage of lower left and right third molar development was observed in each radiograph and a modified Gat score was assigned. Linear regression on this data produced the following equation: Y=9.309+1.673 mG+0.303S (Y=age; mG=modified Gat score; S=sex). In the second part of this study, the predictive accuracy of this equation was evaluated using data from a second set of panoramic radiographs (539 Thai subjects, 9 to 24 years old). Each subject's age was estimated using the above equation and compared against age calculated from a provided date of birth. Estimated and known age data were analyzed using the Pearson correlation coefficient and descriptive statistics. Ages estimated from lower left and lower right third molar development stage were significantly correlated with the known ages (r=0.818, 0.808, respectively, P≤0.01). 50% of age estimates in the second part of the study fell within a range of error of ±1 year, while 75% fell within a range of error of ±2 years. The study found that the equation tends to estimate age accurately when individuals are 9 to 20 years of age. The equation can be used for age estimation for Thai populations when the individuals are 9 to 20 years of age.

  7. Accuracy of an equation for estimating age from mandibular third molar development in a Thai population

    Energy Technology Data Exchange (ETDEWEB)

    Verochana, Karune; Prapayasatok, Sangsom; Janhom, Apirum; Mahasantipiya, Phattaranant May; Korwanich, Narumanas [Faculty of Dentistry, Chiang Mai University, Chiang Mai (Thailand)

    2016-03-15

    This study assessed the accuracy of age estimates produced by a regression equation derived from lower third molar development in a Thai population. The first part of this study relied on measurements taken from panoramic radiographs of 614 Thai patients aged from 9 to 20. The stage of lower left and right third molar development was observed in each radiograph and a modified Gat score was assigned. Linear regression on this data produced the following equation: Y=9.309+1.673 mG+0.303S (Y=age; mG=modified Gat score; S=sex). In the second part of this study, the predictive accuracy of this equation was evaluated using data from a second set of panoramic radiographs (539 Thai subjects, 9 to 24 years old). Each subject's age was estimated using the above equation and compared against age calculated from a provided date of birth. Estimated and known age data were analyzed using the Pearson correlation coefficient and descriptive statistics. Ages estimated from lower left and lower right third molar development stage were significantly correlated with the known ages (r=0.818, 0.808, respectively, P≤0.01). 50% of age estimates in the second part of the study fell within a range of error of ±1 year, while 75% fell within a range of error of ±2 years. The study found that the equation tends to estimate age accurately when individuals are 9 to 20 years of age. The equation can be used for age estimation for Thai populations when the individuals are 9 to 20 years of age.

  8. AN ANALYSIS OF THE SHAPES OF INTERSTELLAR EXTINCTION CURVES. VI. THE NEAR-IR EXTINCTION LAW

    International Nuclear Information System (INIS)

    Fitzpatrick, E. L.; Massa, D.

    2009-01-01

    We combine new observations from the Hubble Space Telescope's Advanced Camera of Survey with existing data to investigate the wavelength dependence of near-IR (NIR) extinction. Previous studies suggest a power law form for NIR extinction, with a 'universal' value of the exponent, although some recent observations indicate that significant sight line-to-sight line variability may exist. We show that a power-law model for the NIR extinction provides an excellent fit to most extinction curves, but that the value of the power, β, varies significantly from sight line to sight line. Therefore, it seems that a 'universal NIR extinction law' is not possible. Instead, we find that as β decreases, R(V) ≡ A(V)/E(B - V) tends to increase, suggesting that NIR extinction curves which have been considered 'peculiar' may, in fact, be typical for different R(V) values. We show that the power-law parameters can depend on the wavelength interval used to derive them, with the β increasing as longer wavelengths are included. This result implies that extrapolating power-law fits to determine R(V) is unreliable. To avoid this problem, we adopt a different functional form for NIR extinction. This new form mimics a power law whose exponent increases with wavelength, has only two free parameters, can fit all of our curves over a longer wavelength baseline and to higher precision, and produces R(V) values which are consistent with independent estimates and commonly used methods for estimating R(V). Furthermore, unlike the power-law model, it gives R(V)s that are independent of the wavelength interval used to derive them. It also suggests that the relation R(V) = -1.36 E(K-V)/(E(B-V)) - 0.79 can estimate R(V) to ±0.12. Finally, we use model extinction curves to show that our extinction curves are in accord with theoretical expectations, and demonstrate how large samples of observational quantities can provide useful constraints on the grain properties.

  9. Pramana – Journal of Physics | Indian Academy of Sciences

    Indian Academy of Sciences (India)

    Home; Journals; Pramana – Journal of Physics; Volume 62; Issue 5. Molar extinction coefficients of solutions of some organic compounds. Kulwant Singh G K Sandhu B S Lark. Brief Reports Volume 62 Issue 5 May 2004 pp 1139-1145 ... Keywords. Molar extinction coefficients; effective atomic numbers; electron density.

  10. Extinction of Chained Instrumental Behaviors: Effects of Procurement Extinction on Consumption Responding

    Science.gov (United States)

    Thrailkill, Eric A.; Bouton, Mark E.

    2015-01-01

    Instrumental behavior often consists of sequences or chains of responses that minimally include procurement behaviors that enable subsequent consumption behaviors. In such chains, behavioral units are linked by access to one another and eventually to a primary reinforcer, such as food or a drug. The present experiments examined the effects of extinguishing procurement responding on consumption responding after training of a discriminated heterogeneous instrumental chain. Rats learned to make a procurement response (e.g., pressing a lever) in the presence of a distinctive discriminative stimulus; making that response led to the presentation of a second discriminative stimulus that set the occasion for a consumption response (e.g., pulling a chain), which then produced a food-pellet reinforcer. Experiment 1 showed that extinction of either the full procurement-consumption chain or procurement alone weakened the consumption response tested in isolation. Experiment 2 replicated the procurement extinction effect and further demonstrated that the opportunity to make the procurement response, as opposed to simple exposure to the procurement stimulus alone, was required. In Experiment 3, rats learned 2 distinct discriminated heterogeneous chains; extinction of 1 procurement response specifically weakened the consumption response that had been associated with it. The results suggest that learning to inhibit the procurement response may produce extinction of consumption responding through mediated extinction. The experiments suggest the importance of an associative analysis of instrumental behavior chains. PMID:25915751

  11. Probabilistic optimization of safety coefficients

    International Nuclear Information System (INIS)

    Marques, M.; Devictor, N.; Magistris, F. de

    1999-01-01

    This article describes a reliability-based method for the optimization of safety coefficients defined and used in design codes. The purpose of the optimization is to determine the partial safety coefficients which minimize an objective function for sets of components and loading situations covered by a design rule. This objective function is a sum of distances between the reliability of the components designed using the safety coefficients and a target reliability. The advantage of this method is shown on the examples of the reactor vessel, a vapour pipe and the safety injection circuit. (authors)

  12. Orthodontic space closure after first molar extraction without skeletal anchorage.

    Science.gov (United States)

    Jacobs, Collin; Jacobs-Müller, Claudia; Luley, Carolin; Erbe, Christina; Wehrbein, Heiner

    2011-03-01

    The aim of the study was an analysis of effects and side-effects during mesialization of second molars after extraction of the first permanent molars using the anterior dentition/premolars (PM) as an anchorage unit. A total of 35 patients were examined retrospectively who had undergone unilateral or bilateral first permanent molar extraction in the upper or lower arch due to carious lesions. Space closure was carried out in all cases through mesialization of the second molar using an elastic chain fixed to an edgewise stainless steel archwire and tying the anterior dentition/PM together with a continuous laceback ligature. Tooth movement was assessed from lateral cephalograms, orthopantomograms (OPGs) and images of the patient's study casts taken before and after the end of therapy. Space closure after first molar extractions by mesialization of the second molars without skeletal anchorage was largely achieved by bodily forward movement of the teeth, including a small tipping component or tooth-uprighting component when molars were already mesially inclined. Unilateral and bilateral mesialization of the second molars led to retrusion in the maxilla and mandible [(∆incl.=-3.6° (max., bil.), ∆incl.=-4.2° (mand., bil.)] and to translational retraction [(∆s=-2.3 mm (max., bil.), ∆s=-1.6 mm (mand., bil.)] of the incisors. Examination of the soft tissues revealed an increased posterior displacement of the upper and lower lips to the esthetic line [(∆s=-2.8 mm (max. bil.), ∆s=-2.2 mm (mand., bil.)]. In cases of unilateral mesialization less than 50% of the patients had a slight midline deviation in the mandible towards the extraction side. Side effects during mesialization of the second molars without skeletal anchorage in the anterior dentition/PM were observed primarily affecting the incisors integrated into the anterior anchorage unit. These side-effects resulted in posterior displacement of the soft tissues, including a change in profile. This must be

  13. Histopathologic Evaluation of Follicular Tissues Associated with Impacted Third Molars

    Directory of Open Access Journals (Sweden)

    M. Khorasani

    2008-06-01

    Full Text Available Objective: The aim of the present study was to histopathologically evaluate follicular tissues of third molars with pericoronal radiolucenciesof less than 2 millimeters.Materials and Methods: In this descriptive analytic study, 100 impacted third molars with normal follicular spaces were removed and their pericoronaltissues submitted for histopathologic examination. Different characteristicsof the epithelium and connective tissue were evaluated in all cases. Statisti-cal analysis was performed using chi square and Mann-Whitney tests.Results: In our study sample, 74% of the patients were female and 26% were male, ranging in age from 13 to 54 years (mean, 25.3 years. Lining epithelium was observed in 69% of the specimens of which 31%, 23% and 14% was cuboidal, squamous and columnar, respectively. A significant re-lationship was found between the presence of squamous epithelium and pa-tient age (P<0.05. Nonspecific chronic inflammation was the only patho-logic finding observed in 44% of the specimens. Inflammation was signifi-cantly associated with age and squamous metaplasia (P<0.05.Conclusion: Considering that pathologic lesions were not observed in anyof the studied cases, unerupted third molars should not be removed unless there is a clinical indication to do so, or in case the impacted molar shows evidence of pathological changes. Follow-up is suggested for asympto-matic impacted third molars.

  14. Adhesives for bonded molar tubes during fixed brace treatment.

    Science.gov (United States)

    Millett, Declan T; Mandall, Nicky A; Mattick, Rye Cr; Hickman, Joy; Glenny, Anne-Marie

    2017-02-23

    Orthodontic treatment involves using fixed or removable appliances (dental braces) to correct the positions of teeth. The success of a fixed appliance depends partly on the metal attachments (brackets and bands) being glued to the teeth so that they do not become detached during treatment. Brackets (metal squares) are usually attached to teeth other than molars, where bands (metal rings that go round each tooth) are more commonly used. Orthodontic tubes (stainless steel tubes that allow wires to pass through them), are typically welded to bands but they may also be glued directly (bonded) to molars. Failure of brackets, bands and bonded molar tubes slows down the progress of treatment with a fixed appliance. It can also be costly in terms of clinical time, materials and time lost from education/work for the patient. This is an update of the Cochrane review first published in 2011. A new full search was conducted on 15 February 2017 but no new studies were identified. We have only updated the search methods section in this new version. The conclusions of this Cochrane review remain the same. To evaluate the effectiveness of the adhesives used to attach bonded molar tubes, and the relative effectiveness of the adhesives used to attach bonded molar tubes versus adhesives used to attach bands, during fixed appliance treatment, in terms of: (1) how often the tubes (or bands) come off during treatment; and (2) whether they protect the bonded (or banded) teeth against decay. The following electronic databases were searched: Cochrane Oral Health's Trials Register (to 15 February 2017), the Cochrane Central Register of Controlled Trials (CENTRAL; 2017, Issue 1) in the Cochrane Library (searched 15 February 2017), MEDLINE Ovid (1946 to 15 February 2017), and Embase Ovid (1980 to 15 February 2017). We searched ClinicalTrials.gov and the World Health Organization International Clinical Trials Registry Platform for ongoing trials. No restrictions were placed on the language or

  15. Elective extractions of first permanent molars: a review

    Directory of Open Access Journals (Sweden)

    Melike Kiraz

    2018-05-01

    Full Text Available Permanent first molar teeth possess a key role in the setting-up of the occlusion, contribute significantly to the chewing function and serve as a guide for other teeth. However, it is frequently encountered that permanent first molar teeth are extracted due to the predicted negative prognoses of caries or developmental defects. As a result of the uncontrolled extraction of the permanent first molar teeth during the growth and development period, drifting of adjacent teeth, continued eruption of the opposing teeth and displacements can be seen. Furthermore, following one-sided extraction, midline deviations, oppositional tooth eruption, skeletal and dental asymmetry, unilateral chewing habits, and temporo-mandibular joint disorders may occur. To prevent these pathological conditions and to maintain the stability of the occlusal relation, it is necessary to do compensation and balancing extractions of the permanent first molar teeth on the opposite/symmetric arc, assuming mesial drag of the permanent second and third molar teeth. With such controlled-extractions, especially in Class I cases, orthodontic or prosthetic treatments, which may require extra time, cost and effort, could be prevented and a conceivable occlusion can be established.

  16. Requirement of alveolar bone formation for eruption of rat molars

    Science.gov (United States)

    Wise, Gary E.; He, Hongzhi; Gutierrez, Dina L.; Ring, Sherry; Yao, Shaomian

    2011-01-01

    Tooth eruption is a localized event that requires a dental follicle (DF) to regulate the resorption of alveolar bone to form an eruption pathway. During the intra-osseous phase of eruption, the tooth moves through this pathway. The mechanism or motive force that propels the tooth through this pathway is controversial but many studies have shown that alveolar bone growth at the base of the crypt occurs during eruption. To determine if this bone growth (osteogenesis) was causal, experiments were designed in which the expression of an osteogenic gene in the DF, bone morphogenetic protein-6 (BMP6), was inhibited by injection of the 1st mandibular molar of the rat with an siRNA targeted against BMP6. The injection was followed by electroporation to promote uptake of the siRNA. In 45 first molars injected, eruption either was delayed or completely inhibited (7 molars). In the impacted molars, an eruption pathway formed but bone growth at the base of the crypt was greatly reduced as compared to the erupted first molar controls. These studies show that alveolar bone growth at the base of the crypt is required for tooth eruption and that BMP6 may be an essential gene for promoting this growth. PMID:21896048

  17. Lingual nerve injury following surgical removal of mandibular third molar

    Directory of Open Access Journals (Sweden)

    Abduljaleel Azad Samad

    2017-12-01

    Full Text Available Background and objective: The close proximity of lingual nerve in relation to the lingual cortical bone of the posterior mandibular third molar is clinically important because lingual nerve may be subjected to trauma during surgical removal of the impacted lower third molar. This prospective study aimed to evaluate the incidence of lingual nerve paresthesia following surgical removal of mandibular third molar in College of Dentistry, Hawler Medical University. Methods: A total of 116 third molars surgery were carried out under local anesthesia for 116 patients for removal of lower mandibular teeth Using Terence Ward's incision made in all cases, and after that, the buccal flap was reflected, lingual tissues had been retracted during bone removal with a periosteal elevator. The sensory disturbance was evaluated on the 7th postoperative day by standard questioning the patients: “Do you have any unusual feeling in your tongue, lingual gingiva and mucosa of the floor of the mouth?" Results: One patient experienced sensory disturbance, the lingual nerve paresthesia incidence was 0.9% as a transient sensory disturbance, while no patient of permanent sensory disturbance. Conclusion: The incidence of injury to the lingual nerve can be minimized by careful clinical evaluation, surgeon’s experience, surgical approach and knowledge about anatomical landmarks during surgical removal of an impacted lower third molar tooth.

  18. Western Saudi adolescent age estimation utilising third molar development.

    Science.gov (United States)

    Alshihri, Amin M; Kruger, Estie; Tennant, Marc

    2014-07-01

    The aim of this study was to establish reference data on third molar morphology/development for age estimation in Western Saudi adolescents, between ages 14 and 23 years of old. The orthopantomograms of 130 individuals (males and females), were examined, and the stage of third molar development were evaluated. Mean ages, standard deviations, and percentile distributions are presented for each stage of development. The mean estimated age for all participants (n = 130) was 219.7 months, and this differed significantly (P age (226.5 months). Deviations of predicted age from real age showed 28.5% of all participants had their age estimated within 1 year (±12 months) of their chronological age. Most (43%) had their age underestimated by more than 12 months and the remaining 28.5% had their age overestimated by more than 12 months of their chronological age. Differences in left-right symmetry information of third molars were detected and were higher in the maxilla (92%) than in the mandible (82%). For all molars reaching stage "H" most individuals (males and females) were over the age 18 years of old. Males reach the developmental stages earlier than females. Third molar tooth development can be reliably used to generate mean age and the estimated age range for an individual of unknown chronological age. Further studies with large populations are needed for better statistical results.

  19. Age of patient at the extraction of the third molar.

    Science.gov (United States)

    Kautto, A; Vehkalahti, M M; Ventä, I

    2018-04-13

    The purpose of this study was to assess the age of patients at the time of extraction of third molars. Our data included all routine and surgical extractions of third molars (n=8199 teeth) performed by general and specialist dentists of the public oral health services of the city of Helsinki over the period 2013-2014. Measurements included patient's age, gender, the identified third molar, the type of anaesthesia, the method of extraction, and the diagnosis at extraction. Patients' ages ranged from 10 to 99years. We found significant differences between younger and older age groups: third molar extractions occurred more often for women than for men below the age of 30years (Page of 40years, but the corresponding prevalences reversed after the age of 40years. Diagnoses at extraction differed between younger and older patients. We conclude that the treatment pattern of third molars at public health services varies greatly over a lifetime, and that a greater variety exists than had been reported previously from oral and maxillofacial units. Copyright © 2018 International Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved.

  20. Autologous Platelet-rich Plasma after Third Molar Surgery.

    Science.gov (United States)

    Gandevivala, Adil; Sangle, Amit; Shah, Dinesh; Tejnani, Avneesh; Sayyed, Aatif; Khutwad, Gaurav; Patel, Arpit Arunbhai

    2017-01-01

    The aim of this study is to compare the efficacy of autologous platelet-rich plasma (PRP) in the third molar impactions, with respect to: pain, swelling, healing, and periodontal status distal to the second molar in patients who need surgical removal of bilateral impacted mandibular third molars. Twenty-five patients of both sexes aged between 16 and 60 years who required bilateral surgical removal of their impacted third molars and met the inclusion criteria were included in the study. After surgical extraction of the third molar, primary closure was performed in the control group, whereas PRP was placed in the socket followed by primary closure in the case group. The outcome variables were pain, swelling, wound healing, and periodontal probe depth that were follow-up period of 2 months. Quantitative data are presented as mean. Statistical significance was checked by t -test. There was a difference in the pain (0.071) and facial swelling (0.184), reduction between test and control on day 3, but it was not found to be significant. Periodontal pocket depth (0.001) and wound healing (0.001) less in case group compared with the control group was found to be significant. The use of PRP lessens the severity of immediate postoperative sequelae and decreases preoperative pocket depth.

  1. Buoyancy Effect of Ionic Vacancy on the Change of the Partial Molar Volume in Ferricyanide-Ferrocyanide Redox Reaction under a Vertical Gravity Field

    Directory of Open Access Journals (Sweden)

    Yoshinobu Oshikiri

    2013-01-01

    Full Text Available With a gravity electrode (GE in a vertical gravity field, the buoyancy effect of ionic vacancy on the change of the partial molar volume in the redox reaction between ferricyanide (FERRI and ferrocyanide (FERRO ions was examined. The buoyancy force of ionic vacancy takes a positive or negative value, depending on whether the rate-determining step is the production or extinction of the vacancy. Though the upward convection over an upward electrode in the FERRO ion oxidation suggests the contribution of the positive buoyancy force arising from the vacancy production, the partial molar volume of the vacancy was not measured. On the other hand, for the downward convection under a downward electrode in the FERRI ion reduction, it was not completely but partly measured by the contribution of the negative buoyancy force from the vacancy extinction. Since the lifetime of the vacancy is decreased by the collision between ionic vacancies during the convection, the former result was ascribed to the shortened lifetime due to the increasing collision efficiency in the enhanced upward convection over an upward electrode, whereas the latter was thought to arise from the elongated lifetime due to the decreasing collision efficiency by the stagnation under the downward electrode.

  2. The third molar maturity index in indicating the legal adult age in Kosovar population.

    Science.gov (United States)

    Kelmendi, Jeta; Cameriere, Roberto; Koçani, Ferit; Galić, Ivan; Mehmeti, Blerim; Vodanović, Marin

    2017-12-16

    The third molar tooth, known as the "wisdom tooth," is the only tooth that can be used to determine legal adult age. This study aimed to test the accuracy of Cameriere's third molar maturity index (I 3M ) in assessing the legal adult age of 18 years in the Kosovar population. Orthopantomographs (OPTs) of 1221 healthy living Kosovar individuals, aged between 12 and 23 years and with no congenital or developmental anomalies, were analyzed. Intra-class correlation coefficients were 0.858 (95% CI, 0.786 to 0.906) and 0.852 (95% CI, 0.779 to 0.903) for intra-rater and for inter-rater agreement, respectively. The sample was divided into training dataset (800 OPTs) and test dataset (421 OPTs). The training dataset was used to generate the logistic regression model, while the test dataset was used to study the performance of the model. I 3M and gender as independent variables and adult age (≥ 18 years) or minor age (age. The results showed that only I 3M statistically significantly contributed to discriminating adults and minors. ROC analysis showed that the cut-off value of I 3M  age gradually increased. The performance of the cut-off value of I 3M  age in a Kosovar population.

  3. Measurement of the molar heat capacities of MoO2 and MoO3 from 350 to 950 K

    International Nuclear Information System (INIS)

    Inaba, H.; Miyahara, K.; Naito, K.

    1984-01-01

    Molar heat capacities of MoO 2 and MoO 3 were measured in the range between 350 and 950 K by means of adiabatic scanning calorimetry. For MoO 2 , a sharp heat-capacity anomaly with a molar enthalpy change of (178 +- 24) J.mol -1 and a molar entropy change of (0.207 +- 0.028) J.K -1 .mol -1 was observed at 865 K, which had not been detected by drop calorimetry. For MoO 3 , two heat-capacity anomalies with molar enthalpy changes of (88 +- 21) and (60 +- 36) J.mol -1 were found at 808 K and 857 K, respectively; neither anomaly had been detected by the drop method. The lattice molar heat capacities of MoO 2 and MoO 3 are estimated as Csub(l,m)(MoO 2 ) = D(469 K/T) + E(578 K/T) + E(876 K/T) and Csub(l,m)(MoO 3 ) = D(208 K/T) + 2E(488 K/T) + E(1170 K/T), where D(x) and E(x) are the Debye and Einstein functions, respectively. The temperature coefficient of the electronic molar heat capacity of MoO 2 is estimated as (6.0 +- 0.5) mJ.K -2 .mol -1 . The excess heat capacity in MoO 3 found at higher temperatures is interpreted as being due to vacancy formation with a molar activation energy of (98 +-5) kJ.mol -1 . The origin of the heat-capacity anomalies is inferred as arising from the slight movement of distorted MoO 6 octahedra in the MoO 2 and MoO 3 structures. (author)

  4. Quadrature formulas for Fourier coefficients

    KAUST Repository

    Bojanov, Borislav; Petrova, Guergana

    2009-01-01

    We consider quadrature formulas of high degree of precision for the computation of the Fourier coefficients in expansions of functions with respect to a system of orthogonal polynomials. In particular, we show the uniqueness of a multiple node

  5. Diffusion coefficient for anomalous transport

    International Nuclear Information System (INIS)

    1986-01-01

    A report on the progress towards the goal of estimating the diffusion coefficient for anomalous transport is given. The gyrokinetic theory is used to identify different time and length scale inherent to the characteristics of plasmas which exhibit anomalous transport

  6. One extinct turtle species less: Pelusios seychellensis is not extinct, it never existed.

    Directory of Open Access Journals (Sweden)

    Heiko Stuckas

    Full Text Available Pelusios seychellensis is thought to be a freshwater turtle species endemic to the island of Mahé, Seychelles. There are only three museum specimens from the late 19(th century known. The species has been never found again, despite intensive searches on Mahé. Therefore, P. seychellensis has been declared as "Extinct" by the IUCN and is the sole putatively extinct freshwater turtle species. Using DNA sequences of three mitochondrial genes of the historical type specimen and phylogenetic analyses including all other species of the genus, we provide evidence that the description of P. seychellensis was erroneously based on a widely distributed West African species, P. castaneus. Consequently, we synonymize the two species and delete P. seychellensis from the list of extinct chelonian species and from the faunal list of the Seychelles.

  7. Fuel Temperature Coefficient of Reactivity

    Energy Technology Data Exchange (ETDEWEB)

    Loewe, W.E.

    2001-07-31

    A method for measuring the fuel temperature coefficient of reactivity in a heterogeneous nuclear reactor is presented. The method, which is used during normal operation, requires that calibrated control rods be oscillated in a special way at a high reactor power level. The value of the fuel temperature coefficient of reactivity is found from the measured flux responses to these oscillations. Application of the method in a Savannah River reactor charged with natural uranium is discussed.

  8. Properties of Traffic Risk Coefficient

    Science.gov (United States)

    Tang, Tie-Qiao; Huang, Hai-Jun; Shang, Hua-Yan; Xue, Yu

    2009-10-01

    We use the model with the consideration of the traffic interruption probability (Physica A 387(2008)6845) to study the relationship between the traffic risk coefficient and the traffic interruption probability. The analytical and numerical results show that the traffic interruption probability will reduce the traffic risk coefficient and that the reduction is related to the density, which shows that this model can improve traffic security.

  9. A window of vulnerability: impaired fear extinction in adolescence.

    Science.gov (United States)

    Baker, Kathryn D; Den, Miriam L; Graham, Bronwyn M; Richardson, Rick

    2014-09-01

    There have been significant advances made towards understanding the processes mediating extinction of learned fear. However, despite being of clear theoretical and clinical significance, very few studies have examined fear extinction in adolescence, which is often described as a developmental window of vulnerability to psychological disorders. This paper reviews the relatively small body of research examining fear extinction in adolescence. A prominent finding of this work is that adolescents, both humans and rodents, exhibit a marked impairment in extinction relative to both younger (e.g., juvenile) and older (e.g., adult) groups. We then review some potential mechanisms that could produce the striking extinction deficit observed in adolescence. For example, one neurobiological candidate mechanism for impaired extinction in adolescence involves changes in the functional connectivity within the fear extinction circuit, particularly between prefrontal cortical regions and the amygdala. In addition, we review research on emotion regulation and attention processes that suggests that developmental changes in attention bias to threatening cues may be a cognitive mechanism that mediates age-related differences in extinction learning. We also examine how a differential reaction to chronic stress in adolescence impacts upon extinction retention during adolescence as well as in later life. Finally, we consider the findings of several studies illustrating promising approaches that overcome the typically-observed extinction impairments in adolescent rodents and that could be translated to human adolescents. Copyright © 2013 Elsevier Inc. All rights reserved.

  10. Cortisol modifies extinction learning of recently acquired fear in men

    Science.gov (United States)

    Hermann, Andrea; Stark, Rudolf; Wolf, Oliver Tobias

    2014-01-01

    Exposure therapy builds on the mechanism of fear extinction leading to decreased fear responses. How the stress hormone cortisol affects brain regions involved in fear extinction in humans is unknown. For this reason, we tested 32 men randomly assigned to receive either 30 mg hydrocortisone or placebo 45 min before fear extinction. In fear acquisition, a picture of a geometrical figure was either partially paired (conditioned stimulus; CS+) or not paired (CS−) with an electrical stimulation (unconditioned stimulus; UCS). In fear extinction, each CS was presented again, but no UCS occurred. Cortisol increased conditioned skin conductance responses in early and late extinction. In early extinction, higher activation towards the CS− than to the CS+ was found in the amygdala, hippocampus and posterior parahippocampal gyrus. This pattern might be associated with the establishment of a new memory trace. In late extinction, the placebo compared with the cortisol group displayed enhanced CS+/CS− differentiation in the amygdala, medial frontal cortex and nucleus accumbens. A change from early deactivation to late activation of the extinction circuit as seen in the placebo group seems to be needed to enhance extinction and to reduce fear. Cortisol appears to interfere with this process thereby impairing extinction of recently acquired conditioned fear. PMID:23945999

  11. Comparison of micro-computerized tomography and cone-beam computerized tomography in the detection of accessory canals in primary molars.

    Science.gov (United States)

    Acar, Buket; Kamburoğlu, Kıvanç; Tatar, İlkan; Arıkan, Volkan; Çelik, Hakan Hamdi; Yüksel, Selcen; Özen, Tuncer

    2015-12-01

    This study was performed to compare the accuracy of micro-computed tomography (CT) and cone-beam computed tomography (CBCT) in detecting accessory canals in primary molars. Forty-one extracted human primary first and second molars were embedded in wax blocks and scanned using micro-CT and CBCT. After the images were taken, the samples were processed using a clearing technique and examined under a stereomicroscope in order to establish the gold standard for this study. The specimens were classified into three groups: maxillary molars, mandibular molars with three canals, and mandibular molars with four canals. Differences between the gold standard and the observations made using the imaging methods were calculated using Spearman's rho correlation coefficient test. The presence of accessory canals in micro-CT images of maxillary and mandibular root canals showed a statistically significant correlation with the stereomicroscopic images used as a gold standard. No statistically significant correlation was found between the CBCT findings and the stereomicroscopic images. Although micro-CT is not suitable for clinical use, it provides more detailed information about minor anatomical structures. However, CBCT is convenient for clinical use but may not be capable of adequately analyzing the internal anatomy of primary teeth.

  12. Comparison of micro-computerized tomography and cone-beam computerized tomography in the detection of accessory canals in primary molars

    Energy Technology Data Exchange (ETDEWEB)

    Acar, Buket; Kamburoglu, Kivanc [Dept. of Dentomaxillofacial Radiology, Faculty of Dentistry, Ankara University, Ankara (Turkmenistan); Tatar, Ilkan [Dept. of Anatomy, Faculty of Medicine, Hacettepe University, Ankara (Turkmenistan); Arikan, Volkan [Dept. of Anatomy, Faculty of Medicine, Hacettepe University, Ankara (Turkmenistan); Celik, Hakan Hamid [Dept. of Pediatric Dentistry, Faculty of Dentistry, Kirikkale Unversity, Ankara (Turkmenistan); Yuksel, Selcen [Dept. of Biostatistics, Faculty of Medicine, Yildirim Beyazit University, Ankara (Turkmenistan); Ozen, Tuncer [Dept. of Dentomaxillofacial Radiology, Gulhane Military Hospital, Dental Clinics, Ankara (Turkmenistan)

    2015-12-15

    This study was performed to compare the accuracy of micro-computed tomography (CT) and cone-beam computed tomography (CBCT) in detecting accessory canals in primary molars. Forty-one extracted human primary first and second molars were embedded in wax blocks and scanned using micro-CT and CBCT. After the images were taken, the samples were processed using a clearing technique and examined under a stereomicroscope in order to establish the gold standard for this study. The specimens were classified into three groups: maxillary molars, mandibular molars with three canals, and mandibular molars with four canals. Differences between the gold standard and the observations made using the imaging methods were calculated using Spearman's rho correlation coefficient test. The presence of accessory canals in micro-CT images of maxillary and mandibular root canals showed a statistically significant correlation with the stereomicroscopic images used as a gold standard. No statistically significant correlation was found between the CBCT findings and the stereomicroscopic images.Although micro-CT is not suitable for clinical use, it provides more detailed information about minor anatomical structures. However, CBCT is convenient for clinical use but may not be capable of adequately analyzing the internal anatomy of primary teeth.

  13. Comparison of micro-computerized tomography and cone-beam computerized tomography in the detection of accessory canals in primary molars

    International Nuclear Information System (INIS)

    Acar, Buket; Kamburoglu, Kivanc; Tatar, Ilkan; Arikan, Volkan; Celik, Hakan Hamid; Yuksel, Selcen; Ozen, Tuncer

    2015-01-01

    This study was performed to compare the accuracy of micro-computed tomography (CT) and cone-beam computed tomography (CBCT) in detecting accessory canals in primary molars. Forty-one extracted human primary first and second molars were embedded in wax blocks and scanned using micro-CT and CBCT. After the images were taken, the samples were processed using a clearing technique and examined under a stereomicroscope in order to establish the gold standard for this study. The specimens were classified into three groups: maxillary molars, mandibular molars with three canals, and mandibular molars with four canals. Differences between the gold standard and the observations made using the imaging methods were calculated using Spearman's rho correlation coefficient test. The presence of accessory canals in micro-CT images of maxillary and mandibular root canals showed a statistically significant correlation with the stereomicroscopic images used as a gold standard. No statistically significant correlation was found between the CBCT findings and the stereomicroscopic images.Although micro-CT is not suitable for clinical use, it provides more detailed information about minor anatomical structures. However, CBCT is convenient for clinical use but may not be capable of adequately analyzing the internal anatomy of primary teeth

  14. Candesartan ameliorates impaired fear extinction induced by innate immune activation.

    Science.gov (United States)

    Quiñones, María M; Maldonado, Lizette; Velazquez, Bethzaly; Porter, James T

    2016-02-01

    Patients with post-traumatic stress disorder (PTSD) tend to show signs of a relatively increased inflammatory state suggesting that activation of the immune system may contribute to the development of PTSD. In the present study, we tested whether activation of the innate immune system can disrupt acquisition or recall of auditory fear extinction using an animal model of PTSD. Male adolescent rats received auditory fear conditioning in context A. The next day, an intraperitoneal injection of lipopolysaccharide (LPS; 100 μg/kg) prior to auditory fear extinction in context B impaired acquisition and recall of extinction. LPS (100 μg/kg) given after extinction training did not impair extinction recall suggesting that LPS did not affect consolidation of extinction. In contrast to cued fear extinction, contextual fear extinction was not affected by prior injection of LPS (100 μg/kg). Although LPS also reduced locomotion, we could dissociate the effects of LPS on extinction and locomotion by using a lower dose of LPS (50 μg/kg) which impaired locomotion without affecting extinction. In addition, 15 h after an injection of 250 μg/kg LPS in adult rats, extinction learning and recall were impaired without affecting locomotion. A sub-chronic treatment with candesartan, an angiotensin II type 1 receptor blocker, prevented the LPS-induced impairment of extinction in adult rats. Our results demonstrate that activation of the innate immune system can disrupt auditory fear extinction in adolescent and adult animals. These findings also provide direction for clinical studies of novel treatments that modulate the innate immune system for stress-related disorders like PTSD. Copyright © 2015 Elsevier Inc. All rights reserved.

  15. Standard molar enthalpies of formation of monochloroacetophenone isomers

    International Nuclear Information System (INIS)

    Ribeiro da Silva, Manuel A.V.; Amaral, Luisa M.P.F.

    2010-01-01

    The standard (p 0 =0.1MPa) molar enthalpies of formation of the liquids 2'-, 3'-, and 4'-chloroacetophenones were derived from the standard molar energies of combustion, in oxygen, to yield CO 2 (g) and HCl . 600H 2 O(l), at T = 298.15 K, measured by rotating-bomb combustion calorimetry. The Calvet microcalorimetry was used to measure the enthalpies of vaporization of the three compounds. These two thermodynamic parameters yielded the standard molar enthalpies of formation of the chloroacetophenone isomers, in the gaseous phase, at T = 298.15 K. (table) An empirical scheme, developed by Cox, was used to estimate the gas-phase enthalpies of formation and the obtained values were compared with the experimental ones.

  16. COMPLICATIONS AFTER EXTRACTION OF IMPACTED THIRD MOLARS - LITERATURE REVIEW

    Directory of Open Access Journals (Sweden)

    Elitsa G. Deliverska

    2016-07-01

    Full Text Available Third molar surgery is the most common procedure performed by oral and maxillofacial surgeons worldwide. This article addresses the incidence of specific complications and, where possible, offers a preventive or management strategy. Complications, such as pain, dry socket, swelling, paresthesia of the lingual or inferior alveolar nerve, bleeding, and infection are most common. Factors thought to influence the incidence of complications after third molar removal include age, gender, medical history, oral contraceptives, presence of pericoronitis, poor oral hygiene, smoking, type of impaction, relationship of third molar to the inferior alveolar nerve, surgical time, surgical technique, surgeon experience, use of perioperative antibiotics, use of topical antiseptics, use of intra-socket medications, and anaesthetic technique. For the general dental practitioner, as well as the oral and maxillofacial surgeon, it is important to be familiar with all the possible complications after this procedure. This improves patient education and leads to prevention, early recognition and management.

  17. Standard molar enthalpies of formation of monochloroacetophenone isomers

    Energy Technology Data Exchange (ETDEWEB)

    Ribeiro da Silva, Manuel A.V., E-mail: risilva@fc.up.p [Centro de Investigacao em Quimica, Department of Chemistry and Biochemistry, Faculty of Science, University of Porto, Rua do Campo Alegre, 687, P-4169-007 Porto (Portugal); Amaral, Luisa M.P.F. [Centro de Investigacao em Quimica, Department of Chemistry and Biochemistry, Faculty of Science, University of Porto, Rua do Campo Alegre, 687, P-4169-007 Porto (Portugal)

    2010-12-15

    The standard (p{sup 0}=0.1MPa) molar enthalpies of formation of the liquids 2'-, 3'-, and 4'-chloroacetophenones were derived from the standard molar energies of combustion, in oxygen, to yield CO{sub 2}(g) and HCl . 600H{sub 2}O(l), at T = 298.15 K, measured by rotating-bomb combustion calorimetry. The Calvet microcalorimetry was used to measure the enthalpies of vaporization of the three compounds. These two thermodynamic parameters yielded the standard molar enthalpies of formation of the chloroacetophenone isomers, in the gaseous phase, at T = 298.15 K. (table) An empirical scheme, developed by Cox, was used to estimate the gas-phase enthalpies of formation and the obtained values were compared with the experimental ones.

  18. Pendulum Therapy of Molar Distalization in Mixed Dentition.

    Science.gov (United States)

    Patil, Raju Umaji; Prakash, Amit; Agarwal, Anshu

    2016-01-01

    Early and timely pedo-orthodontic treatment is aimed at eliminating the disturbances of skeletal or dentoalveolar development, to harmonize the stomatognathic system before the full eruption of all permanent teeth. The advantages of pendulum appliance are its minimal dependence on patient's compliance (child cooperation), ease of fabrication, onetime activation and adjustment of the springs if necessary to correct minor transverse and vertical molar positions. This article reports a successful treatment method of class II malocclusion with pendulum appliance in mixed dentition phase. Distalization of maxillary molar was done, followed by guidance of canine impaction orthodontically and other dental correction using 0.022 MBT appliances. Posttreatment results were stable and remarkable. How to cite this article: Patil RU, Prakash A, Agarwal A. Pendulum Therapy of Molar Distalization in Mixed Dentition. Int J Clin Pediatr Dent 2016;9(1):67-73.

  19. La hiperdontia en región de molares Hyperdontia in molar region

    Directory of Open Access Journals (Sweden)

    George Táccio de Miranda Candeiro

    2011-12-01

    Full Text Available La hiperdontia constituye una de las anomalías más estudiadas de la dentición humana. Esa alteración representa la aparición de uno o más dientes en cantidades mayores de lo normal, que puede ocurrir en la mandíbula o maxila y de manera unilateral o bilateral. La etiología de los dientes supernumerarios puede ser explicada principalmente por hiperactividad de la lámina dentaria en la fase inicial. Es importante la detección precoz de dientes supernumerarios porque se ha visto una serie de complicaciones como los diastemas, que pueden causar en la cavidad bucal: retardo de la erupción o dientes impactados, posicionamiento inadecuado de dientes permanentes, desajuste oclusal y el desarrollo de quistes y tumores odontógenos. Así el diagnóstico es normalmente realizado a partir de un examen radiográfico convencional, principalmente la radiografía panorámica. Este trabajo tuvo como objetivo relatar 4 casos clínicos de pacientes con presencia de molares supernumerarios, que fueron atendidos en el Servicio de Radiología de la Escuela de Odontología de la Universidad Federal de Ceará.Hyperdontia is one of the more studied anomalies of human dentition. This alteration represents the appearance of one or more teeth in a number greater of normal, occurring in mandible or in maxilla and could be unilateral or bilateral. The etiology of supernumerary teeth may be explained mainly due to the hyperactivity of dental plate in its initial phase; its early detection is important because of there have been a series of complications that may to cause diastemata, eruption retard or impacted teeth, inappropriate positioning of permanent teeth, occlusal misalignment and the development of odontogenic cysts or tumors. Thus, the diagnosis is normally made from a conventional radiographic examination, mainly the panoramic X-ray. The objective of present paper is the present four clinical cases of patients presenting with supernumerary molars, seen in

  20. Clustering Coefficients for Correlation Networks.

    Science.gov (United States)

    Masuda, Naoki; Sakaki, Michiko; Ezaki, Takahiro; Watanabe, Takamitsu

    2018-01-01

    Graph theory is a useful tool for deciphering structural and functional networks of the brain on various spatial and temporal scales. The clustering coefficient quantifies the abundance of connected triangles in a network and is a major descriptive statistics of networks. For example, it finds an application in the assessment of small-worldness of brain networks, which is affected by attentional and cognitive conditions, age, psychiatric disorders and so forth. However, it remains unclear how the clustering coefficient should be measured in a correlation-based network, which is among major representations of brain networks. In the present article, we propose clustering coefficients tailored to correlation matrices. The key idea is to use three-way partial correlation or partial mutual information to measure the strength of the association between the two neighboring nodes of a focal node relative to the amount of pseudo-correlation expected from indirect paths between the nodes. Our method avoids the difficulties of previous applications of clustering coefficient (and other) measures in defining correlational networks, i.e., thresholding on the correlation value, discarding of negative correlation values, the pseudo-correlation problem and full partial correlation matrices whose estimation is computationally difficult. For proof of concept, we apply the proposed clustering coefficient measures to functional magnetic resonance imaging data obtained from healthy participants of various ages and compare them with conventional clustering coefficients. We show that the clustering coefficients decline with the age. The proposed clustering coefficients are more strongly correlated with age than the conventional ones are. We also show that the local variants of the proposed clustering coefficients (i.e., abundance of triangles around a focal node) are useful in characterizing individual nodes. In contrast, the conventional local clustering coefficients were strongly